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Номер 485, страница 140 - гдз по алгебре 9 класс учебник Солтан, Солтан
Авторы: Солтан Г. Н., Солтан А. Е., Жумадилова А. Ж.
Тип: Учебник
Издательство: Кокшетау
Год издания: 2019 - 2026
ISBN: 978-601-317-424-2
Рекомендовано Министерством образования и науки Республики Казахстан
Популярные ГДЗ в 9 классе
III. Последовательности. 19. Бесконечно убывающая геометрическая прогрессия - номер 485, страница 140.
App\Models\Task {#1024 // resources/views/models/task/default.blade.php #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1108213 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "140" "field_page_end" => null "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik/1-485" "field_display_title" => "485" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#331 #items: array:1 [ 0 => App\Models\Term {#1029 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 26 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "номер" "field_cases" => array:6 [ "field_accusative_case" => "номер" "field_creative_case" => "номером" "field_dative_case" => "номеру" "field_genitive_case" => "номера" "field_nominative_case" => "номер" "field_prepositional_case" => "номере" ] "field_short_name" => "№" ] #original: array:6 [ "id" => 26 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "номер" "field_cases" => array:6 [ "field_accusative_case" => "номер" "field_creative_case" => "номером" "field_dative_case" => "номеру" "field_genitive_case" => "номера" "field_nominative_case" => "номер" "field_prepositional_case" => "номере" ] "field_short_name" => "№" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1026 #items: [] #escapeWhenCastingToString: false } "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#342 #items: array:1 [ 0 => App\Models\Branch {#1023 #connection: "mysql" #table: "branches" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1107653 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "III. Последовательности" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#333 #items: [] #escapeWhenCastingToString: false } "field_page_start" => "92" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1033 #items: array:1 [ 0 => App\Models\Book {#1030 #connection: "mysql" #table: "books" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:50 [ "id" => 4298 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1032 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1035 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1037 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1039 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1043 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1044 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1046 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1048 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1050 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1051 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1052 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1053 …2} "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1054 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1055 …2} "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1056 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1057 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1058 …2} "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1059 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #original: array:50 [ "id" => 4298 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1032 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1035 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1037 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1039 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1043 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1044 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1046 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1048 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1050 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1051 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1052 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1053 …2} "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1054 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1055 …2} "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1056 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1057 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1058 …2} "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1059 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "branch_parent" => Illuminate\Database\Eloquent\Collection {#1060 #items: [] #escapeWhenCastingToString: false } ] #original: array:24 [ "id" => 1107653 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "III. Последовательности" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#333} "field_page_start" => "92" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1033} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1060} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "parent_branches" => Illuminate\Database\Eloquent\Collection {#1061 #items: array:2 [ 0 => App\Models\Branch {#1062 #connection: "mysql" #table: "branches" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1107653 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "III. Последовательности" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1063 #items: [] #escapeWhenCastingToString: false } "field_page_start" => "92" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1064 #items: array:1 [ 0 => App\Models\Book {#1065 #connection: "mysql" #table: "books" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:50 [ "id" => 4298 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1066 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1068 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1070 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1072 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1076 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1077 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1079 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1081 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1083 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1084 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1085 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1086 …2} "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1087 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1088 …2} "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1089 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1090 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1091 …2} "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1092 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #original: array:50 [ "id" => 4298 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1066 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1068 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1070 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1072 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1076 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1077 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1079 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1081 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1083 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1084 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1085 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1086 …2} "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1087 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1088 …2} "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1089 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1090 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1091 …2} "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1092 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "branch_parent" => Illuminate\Database\Eloquent\Collection {#1093 #items: [] #escapeWhenCastingToString: false } ] #original: array:24 [ "id" => 1107653 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "III. Последовательности" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1063} "field_page_start" => "92" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1064} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1093} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 1 => App\Models\Branch {#1094 #connection: "mysql" #table: "branches" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1107660 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "19. Бесконечно убывающая геометрическая прогрессия" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1095 #items: [] #escapeWhenCastingToString: false } "field_page_start" => "134" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1096 #items: array:1 [ 0 => App\Models\Book {#1097 #connection: "mysql" #table: "books" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:50 [ "id" => 4298 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1098 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1100 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1102 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1104 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1108 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1109 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1111 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1113 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1115 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1116 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1117 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1118 …2} "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1119 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1120 …2} "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1121 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1122 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1123 …2} "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1124 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #original: array:50 [ "id" => 4298 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1098 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1100 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1102 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1104 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1108 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1109 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1111 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1113 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1115 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1116 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1117 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1118 …2} "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1119 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1120 …2} "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1121 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1122 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1123 …2} "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1124 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "branch_parent" => Illuminate\Database\Eloquent\Collection {#1125 #items: array:1 [ 0 => App\Models\Branch {#1126 #connection: "mysql" #table: "branches" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1107653 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "III. Последовательности" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1127 …2} "field_page_start" => "92" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1128 …2} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1157 …2} ] #original: array:24 [ "id" => 1107653 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "III. Последовательности" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1127 …2} "field_page_start" => "92" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1128 …2} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1157 …2} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } ] #original: array:24 [ "id" => 1107660 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "19. Бесконечно убывающая геометрическая прогрессия" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1095} "field_page_start" => "134" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1096} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1125} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "content" => Illuminate\Database\Eloquent\Collection {#1158 #items: array:3 [ 0 => App\Models\Element {#1159 #connection: "mysql" #table: "elements" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:7 [ "id" => 1276840 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1160 #items: array:1 [ 0 => App\Models\Edition {#1161 #connection: "mysql" #table: "editions" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:21 [ "id" => 4953 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Условие" "field_order" => "1" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1162 …2} "field_content_type" => "free" "field_content_mode" => "text, image" "field_page_content_mode" => "image" "field_content_text_checked" => null "field_page_content_text_checked" => "0" "field_solution_author" => "Автор" "field_moderator" => "pasha" "field_edition_type" => "statement" "field_root_dir" => "0-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1164 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1165 …2} "field_process_formula" => "katex" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1166 …2} "field_content_source" => null ] #original: array:21 [ "id" => 4953 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Условие" "field_order" => "1" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1162 …2} "field_content_type" => "free" "field_content_mode" => "text, image" "field_page_content_mode" => "image" "field_content_text_checked" => null "field_page_content_text_checked" => "0" "field_solution_author" => "Автор" "field_moderator" => "pasha" "field_edition_type" => "statement" "field_root_dir" => "0-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1164 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1165 …2} "field_process_formula" => "katex" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1166 …2} "field_content_source" => null ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "task" => array:2 [ "refs" => "1108213" "type" => "task" ] "text" => "<p><strong>485.</strong> Дана бесконечно убывающая геометрическая прогрессия ($c_n$),</p><p>сумма которой равна 8. Причем $c_n = \frac{1}{4}$ и $\frac{c_1 + c_2 + ... + c_{n-1}}{c_{n+1} + c_{n+2} + ...} = 30.$</p><p>Найдите номер члена прогрессии, равного $\frac{1}{4}$.</p>" "img" => array:1 [ 0 => array:5 [ "name" => "485-1.jpg" "alt" => null "width" => "1567" "height" => 404 "path" => "/media/algebra_09/soltan-u19/0-1/485-1.webp?ts=1752834508" ] ] ] #original: array:7 [ "id" => 1276840 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1160} "task" => array:2 [ "refs" => "1108213" "type" => "task" ] "text" => "<p><strong>485.</strong> Дана бесконечно убывающая геометрическая прогрессия ($c_n$),</p><p>сумма которой равна 8. Причем $c_n = \frac{1}{4}$ и $\frac{c_1 + c_2 + ... + c_{n-1}}{c_{n+1} + c_{n+2} + ...} = 30.$</p><p>Найдите номер члена прогрессии, равного $\frac{1}{4}$.</p>" "img" => array:1 [ 0 => array:5 [ "name" => "485-1.jpg" "alt" => null "width" => "1567" "height" => 404 "path" => "/media/algebra_09/soltan-u19/0-1/485-1.webp?ts=1752834508" ] ] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 1 => App\Models\Element {#1167 #connection: "mysql" #table: "elements" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 1278131 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1168 #items: array:1 [ 0 => App\Models\Edition {#1169 #connection: "mysql" #table: "editions" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:21 [ "id" => 4954 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Решение" "field_order" => "2" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1170 …2} "field_content_type" => "free" "field_content_mode" => "image" "field_page_content_mode" => "" "field_content_text_checked" => "0" "field_page_content_text_checked" => "0" "field_solution_author" => "Неизвестный" "field_moderator" => "pasha" "field_edition_type" => "solution" "field_root_dir" => "1-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1172 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1173 …2} "field_process_formula" => "" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1174 …2} "field_content_source" => null ] #original: array:21 [ "id" => 4954 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Решение" "field_order" => "2" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1170 …2} "field_content_type" => "free" "field_content_mode" => "image" "field_page_content_mode" => "" "field_content_text_checked" => "0" "field_page_content_text_checked" => "0" "field_solution_author" => "Неизвестный" "field_moderator" => "pasha" "field_edition_type" => "solution" "field_root_dir" => "1-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1172 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1173 …2} "field_process_formula" => "" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1174 …2} "field_content_source" => null ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "task" => array:2 [ "refs" => "1108213" "type" => "task" ] "img" => array:2 [ 0 => array:5 [ "name" => "485-1.jpg" "alt" => null "width" => "1304" "height" => 563 "path" => "/media/algebra_09/soltan-u19/1-1/485-1.webp?ts=1752831253" ] 1 => array:5 [ "name" => "485-2.jpg" "alt" => null "width" => "1405" "height" => 1344 "path" => "/media/algebra_09/soltan-u19/1-1/485-2.webp?ts=1752831253" ] ] ] #original: array:6 [ "id" => 1278131 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1168} "task" => array:2 [ "refs" => "1108213" "type" => "task" ] "img" => array:2 [ 0 => array:5 [ "name" => "485-1.jpg" "alt" => null "width" => "1304" "height" => 563 "path" => "/media/algebra_09/soltan-u19/1-1/485-1.webp?ts=1752831253" ] 1 => array:5 [ "name" => "485-2.jpg" "alt" => null "width" => "1405" "height" => 1344 "path" => "/media/algebra_09/soltan-u19/1-1/485-2.webp?ts=1752831253" ] ] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 2 => App\Models\Element {#1175 #connection: "mysql" #table: "elements" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 1554086 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1176 #items: array:1 [ 0 => App\Models\Edition {#1177 #connection: "mysql" #table: "editions" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:21 [ "id" => 5665 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Решение 2 (rus)" "field_order" => "3" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1178 …2} "field_content_type" => "free" "field_content_mode" => "text" "field_page_content_mode" => "" "field_content_text_checked" => null "field_page_content_text_checked" => "0" "field_solution_author" => "Gemini 2.5 Pro" "field_moderator" => "tolik" "field_edition_type" => "solution" "field_root_dir" => "2-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1180 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1181 …2} "field_process_formula" => "katex" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1182 …2} "field_content_source" => null ] #original: array:21 [ "id" => 5665 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Решение 2 (rus)" "field_order" => "3" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1178 …2} "field_content_type" => "free" "field_content_mode" => "text" "field_page_content_mode" => "" "field_content_text_checked" => null "field_page_content_text_checked" => "0" "field_solution_author" => "Gemini 2.5 Pro" "field_moderator" => "tolik" "field_edition_type" => "solution" "field_root_dir" => "2-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1180 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1181 …2} "field_process_formula" => "katex" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1182 …2} "field_content_source" => null ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "task" => array:2 [ "refs" => "1108213" "type" => "task" ] "text" => "<p>Пусть $c_1$ — первый член бесконечно убывающей геометрической прогрессии $(c_n)$, а $q$ — её знаменатель. По определению бесконечно убывающей геометрической прогрессии, $|q| < 1$.</p><p>Сумма бесконечно убывающей геометрической прогрессии вычисляется по формуле $S = \frac{c_1}{1-q}$.Из условия задачи известно, что сумма прогрессии равна 8, поэтому мы можем составить первое уравнение:</p><p>$\frac{c_1}{1-q} = 8$</p><p>Из этого уравнения выразим первый член прогрессии $c_1$:</p><p>$c_1 = 8(1-q)$ (1)</p><p>Рассмотрим второе условие, заданное в виде отношения сумм:</p><p>$\frac{c_1 + c_2 + ... + c_{n-1}}{c_{n+1} + c_{n+2} + ...} = 30$</p><p>Числитель этой дроби — это сумма первых $n-1$ членов геометрической прогрессии, $S_{n-1}$. Используем формулу суммы первых $k$ членов $S_k = \frac{c_1(1-q^k)}{1-q}$.Таким образом, числитель равен:</p><p>$S_{n-1} = \frac{c_1(1-q^{n-1})}{1-q}$</p><p>Поскольку мы знаем, что $\frac{c_1}{1-q} = 8$, мы можем подставить это значение в выражение для $S_{n-1}$:</p><p>$S_{n-1} = 8(1-q^{n-1})$</p><p>Знаменатель дроби, $c_{n+1} + c_{n+2} + ...$, представляет собой сумму бесконечно убывающей геометрической прогрессии, которая начинается с члена $c_{n+1}$ и имеет тот же знаменатель $q$. Сумма этого "остатка" прогрессии равна:</p><p>$S_{ост} = \frac{c_{n+1}}{1-q}$</p><p>Используя формулу $n$-го члена $c_k = c_1 q^{k-1}$, выразим $c_{n+1} = c_1 q^n$. Подставим это в формулу для суммы остатка:</p><p>$S_{ост} = \frac{c_1 q^n}{1-q} = q^n \cdot \frac{c_1}{1-q} = q^n \cdot 8 = 8q^n$</p><p>Теперь подставим полученные выражения для числителя и знаменателя в исходное уравнение с отношением:</p><p>$\frac{8(1-q^{n-1})}{8q^n} = 30$</p><p>Сократив на 8, получим:</p><p>$\frac{1-q^{n-1}}{q^n} = 30$</p><p>$1-q^{n-1} = 30q^n$</p><p>$1 = 30q^n + q^{n-1}$</p><p>Вынесем общий множитель $q^{n-1}$ за скобки:</p><p>$1 = q^{n-1}(30q+1)$</p><p>Отсюда можно выразить $q^{n-1}$:</p><p>$q^{n-1} = \frac{1}{30q+1}$ (2)</p><p>Теперь используем третье условие задачи: $c_n = \frac{1}{4}$.По формуле $n$-го члена: $c_n = c_1 q^{n-1}$.</p><p>$c_1 q^{n-1} = \frac{1}{4}$ (3)</p><p>Теперь у нас есть система из трех уравнений (1), (2) и (3). Подставим выражение для $c_1$ из (1) и для $q^{n-1}$ из (2) в уравнение (3):</p><p>$8(1-q) \cdot \frac{1}{30q+1} = \frac{1}{4}$</p><p>Решим полученное уравнение относительно $q$:</p><p>$\frac{8(1-q)}{30q+1} = \frac{1}{4}$</p><p>Используя свойство пропорции (произведение крайних членов равно произведению средних), получаем:</p><p>$4 \cdot 8(1-q) = 1 \cdot (30q+1)$</p><p>$32(1-q) = 30q+1$</p><p>$32 - 32q = 30q+1$</p><p>$31 = 62q$</p><p>$q = \frac{31}{62} = \frac{1}{2}$</p><p>Мы нашли знаменатель прогрессии. Теперь найдем первый член $c_1$, подставив значение $q$ в уравнение (1):</p><p>$c_1 = 8(1-q) = 8(1-\frac{1}{2}) = 8 \cdot \frac{1}{2} = 4$</p><p>Итак, мы определили параметры прогрессии: $c_1 = 4$ и $q = \frac{1}{2}$.Осталось найти номер члена прогрессии $n$, для которого $c_n = \frac{1}{4}$. Воспользуемся формулой $n$-го члена:</p><p>$c_n = c_1 q^{n-1}$</p><p>$\frac{1}{4} = 4 \cdot (\frac{1}{2})^{n-1}$</p><p>Разделим обе части уравнения на 4:</p><p>$\frac{1}{16} = (\frac{1}{2})^{n-1}$</p><p>Представим левую часть как степень числа $\frac{1}{2}$:</p><p>$\frac{1}{16} = \frac{1}{2^4} = (\frac{1}{2})^4$</p><p>Теперь уравнение имеет вид:</p><p>$(\frac{1}{2})^4 = (\frac{1}{2})^{n-1}$</p><p>Так как основания степеней равны, мы можем приравнять их показатели:</p><p>$4 = n-1$</p><p>$n = 5$</p><p>Таким образом, член прогрессии, равный $\frac{1}{4}$, имеет номер 5.</p><p><strong>Ответ:</strong> 5</p>" ] #original: array:6 [ "id" => 1554086 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1176} "task" => array:2 [ "refs" => "1108213" "type" => "task" ] "text" => "<p>Пусть $c_1$ — первый член бесконечно убывающей геометрической прогрессии $(c_n)$, а $q$ — её знаменатель. По определению бесконечно убывающей геометрической прогрессии, $|q| < 1$.</p><p>Сумма бесконечно убывающей геометрической прогрессии вычисляется по формуле $S = \frac{c_1}{1-q}$.Из условия задачи известно, что сумма прогрессии равна 8, поэтому мы можем составить первое уравнение:</p><p>$\frac{c_1}{1-q} = 8$</p><p>Из этого уравнения выразим первый член прогрессии $c_1$:</p><p>$c_1 = 8(1-q)$ (1)</p><p>Рассмотрим второе условие, заданное в виде отношения сумм:</p><p>$\frac{c_1 + c_2 + ... + c_{n-1}}{c_{n+1} + c_{n+2} + ...} = 30$</p><p>Числитель этой дроби — это сумма первых $n-1$ членов геометрической прогрессии, $S_{n-1}$. Используем формулу суммы первых $k$ членов $S_k = \frac{c_1(1-q^k)}{1-q}$.Таким образом, числитель равен:</p><p>$S_{n-1} = \frac{c_1(1-q^{n-1})}{1-q}$</p><p>Поскольку мы знаем, что $\frac{c_1}{1-q} = 8$, мы можем подставить это значение в выражение для $S_{n-1}$:</p><p>$S_{n-1} = 8(1-q^{n-1})$</p><p>Знаменатель дроби, $c_{n+1} + c_{n+2} + ...$, представляет собой сумму бесконечно убывающей геометрической прогрессии, которая начинается с члена $c_{n+1}$ и имеет тот же знаменатель $q$. Сумма этого "остатка" прогрессии равна:</p><p>$S_{ост} = \frac{c_{n+1}}{1-q}$</p><p>Используя формулу $n$-го члена $c_k = c_1 q^{k-1}$, выразим $c_{n+1} = c_1 q^n$. Подставим это в формулу для суммы остатка:</p><p>$S_{ост} = \frac{c_1 q^n}{1-q} = q^n \cdot \frac{c_1}{1-q} = q^n \cdot 8 = 8q^n$</p><p>Теперь подставим полученные выражения для числителя и знаменателя в исходное уравнение с отношением:</p><p>$\frac{8(1-q^{n-1})}{8q^n} = 30$</p><p>Сократив на 8, получим:</p><p>$\frac{1-q^{n-1}}{q^n} = 30$</p><p>$1-q^{n-1} = 30q^n$</p><p>$1 = 30q^n + q^{n-1}$</p><p>Вынесем общий множитель $q^{n-1}$ за скобки:</p><p>$1 = q^{n-1}(30q+1)$</p><p>Отсюда можно выразить $q^{n-1}$:</p><p>$q^{n-1} = \frac{1}{30q+1}$ (2)</p><p>Теперь используем третье условие задачи: $c_n = \frac{1}{4}$.По формуле $n$-го члена: $c_n = c_1 q^{n-1}$.</p><p>$c_1 q^{n-1} = \frac{1}{4}$ (3)</p><p>Теперь у нас есть система из трех уравнений (1), (2) и (3). Подставим выражение для $c_1$ из (1) и для $q^{n-1}$ из (2) в уравнение (3):</p><p>$8(1-q) \cdot \frac{1}{30q+1} = \frac{1}{4}$</p><p>Решим полученное уравнение относительно $q$:</p><p>$\frac{8(1-q)}{30q+1} = \frac{1}{4}$</p><p>Используя свойство пропорции (произведение крайних членов равно произведению средних), получаем:</p><p>$4 \cdot 8(1-q) = 1 \cdot (30q+1)$</p><p>$32(1-q) = 30q+1$</p><p>$32 - 32q = 30q+1$</p><p>$31 = 62q$</p><p>$q = \frac{31}{62} = \frac{1}{2}$</p><p>Мы нашли знаменатель прогрессии. Теперь найдем первый член $c_1$, подставив значение $q$ в уравнение (1):</p><p>$c_1 = 8(1-q) = 8(1-\frac{1}{2}) = 8 \cdot \frac{1}{2} = 4$</p><p>Итак, мы определили параметры прогрессии: $c_1 = 4$ и $q = \frac{1}{2}$.Осталось найти номер члена прогрессии $n$, для которого $c_n = \frac{1}{4}$. Воспользуемся формулой $n$-го члена:</p><p>$c_n = c_1 q^{n-1}$</p><p>$\frac{1}{4} = 4 \cdot (\frac{1}{2})^{n-1}$</p><p>Разделим обе части уравнения на 4:</p><p>$\frac{1}{16} = (\frac{1}{2})^{n-1}$</p><p>Представим левую часть как степень числа $\frac{1}{2}$:</p><p>$\frac{1}{16} = \frac{1}{2^4} = (\frac{1}{2})^4$</p><p>Теперь уравнение имеет вид:</p><p>$(\frac{1}{2})^4 = (\frac{1}{2})^{n-1}$</p><p>Так как основания степеней равны, мы можем приравнять их показатели:</p><p>$4 = n-1$</p><p>$n = 5$</p><p>Таким образом, член прогрессии, равный $\frac{1}{4}$, имеет номер 5.</p><p><strong>Ответ:</strong> 5</p>" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "next" => array:2 [ "refs" => "1108214" "type" => "task" ] "previous" 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=> "Алгебра" "field_abbreviated_name" => null "field_cases" => array:6 [ …6] "field_foreign_lang_name" => null "field_short_name" => null "field_subject_type" => "technical_subject" "field_translit" => "algebra" ] #original: array:10 [ "id" => 6471 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Алгебра" "field_abbreviated_name" => null "field_cases" => array:6 [ …6] "field_foreign_lang_name" => null "field_short_name" => null "field_subject_type" => "technical_subject" "field_translit" => "algebra" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_class" => Illuminate\Database\Eloquent\Collection {#1187 #items: array:1 [ 0 => App\Models\Term {#1188 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 5458 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "9" "field_cases" => array:6 [ …6] "field_translit" => "devjatyj" ] #original: array:6 [ "id" => 5458 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "9" "field_cases" => array:6 [ …6] "field_translit" => "devjatyj" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_publisher" => Illuminate\Database\Eloquent\Collection {#1189 #items: array:1 [ 0 => App\Models\Term {#1190 #connection: "mysql" #table: 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null "field_foreign_lang_surname" => null "field_name" => "Аманбала" "field_patronymic" => "Жумадиловна" "field_surname_rp" => null ] #original: array:12 [ "id" => 7005 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Жумадилова" "field_bio" => null "field_degree_rp" => null "field_foreign_lang_name" => null "field_foreign_lang_patronymic" => null "field_foreign_lang_surname" => null "field_name" => "Аманбала" "field_patronymic" => "Жумадиловна" "field_surname_rp" => null ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1195 #items: [] #escapeWhenCastingToString: false } "field_book_type" => Illuminate\Database\Eloquent\Collection 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#dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_country" => Illuminate\Database\Eloquent\Collection {#1198 #items: array:1 [ 0 => App\Models\Term {#1199 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 6994 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Казахстан" "field_cases" => array:6 [ …6] "field_translit" => "kazakhstan" ] #original: array:6 [ "id" => 6994 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Казахстан" "field_cases" => array:6 [ …6] "field_translit" => "kazakhstan" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_city" => Illuminate\Database\Eloquent\Collection {#1200 #items: array:1 [ 0 => App\Models\Term {#1201 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 6995 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Алматы" "field_cases" => array:6 [ …6] "field_translit" => "almaty" ] #original: array:6 [ "id" => 6995 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Алматы" "field_cases" => array:6 [ …6] "field_translit" => "almaty" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_series" => Illuminate\Database\Eloquent\Collection {#1202 #items: [] #escapeWhenCastingToString: false } "field_umk" => Illuminate\Database\Eloquent\Collection {#1203 #items: [] #escapeWhenCastingToString: false } "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1204 #items: [] #escapeWhenCastingToString: false } "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1205 #items: [] #escapeWhenCastingToString: false } "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1206 #items: [] #escapeWhenCastingToString: false } "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1207 #items: [] #escapeWhenCastingToString: false } "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ 0 => "/media/algebra_09/soltan-u19/covers/cover1.webp?ts=1752140452" ] "field_cover_alts" => array:1 [ 0 => "" ] "field_covers" => array:1 [ 0 => array:4 [ "path" => "/media/algebra_09/soltan-u19/covers/cover1.webp?ts=1752140452" "alt" => "" "width" => "1940" "height" => "2895" ] ] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1208 #items: [] #escapeWhenCastingToString: false } "field_new_book" => Illuminate\Database\Eloquent\Collection {#1209 #items: [] #escapeWhenCastingToString: false } "field_old_book" => Illuminate\Database\Eloquent\Collection {#1210 #items: [] #escapeWhenCastingToString: false } "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1211 #items: [] #escapeWhenCastingToString: false } "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ "class" => 380 "subject" => 542 "class_subject" => 386 ] ] #original: array:50 [ "id" => 4298 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1185} "field_class" => Illuminate\Database\Eloquent\Collection {#1187} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1189} "field_author" => Illuminate\Database\Eloquent\Collection {#1191} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1195} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1196} "field_country" => Illuminate\Database\Eloquent\Collection {#1198} "field_city" => Illuminate\Database\Eloquent\Collection {#1200} "field_series" => Illuminate\Database\Eloquent\Collection {#1202} "field_umk" => Illuminate\Database\Eloquent\Collection {#1203} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1204} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1205} "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1206} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1207} "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ 0 => "/media/algebra_09/soltan-u19/covers/cover1.webp?ts=1752140452" ] "field_cover_alts" => array:1 [ 0 => "" ] "field_covers" => array:1 [ 0 => array:4 [ "path" => "/media/algebra_09/soltan-u19/covers/cover1.webp?ts=1752140452" "alt" => "" "width" => "1940" "height" => "2895" ] ] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1208} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1209} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1210} "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1211} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ "class" => 380 "subject" => 542 "class_subject" => 386 ] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "page" => Illuminate\Database\Eloquent\Collection {#2373 #items: array:1 [ 0 => App\Models\BookPage {#1215 #connection: "mysql" #table: "book_pages" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:21 [ "id" => 1097882 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "140" "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik/page-140" "field_display_title" => "140" "field_folder" => "folder1" "field_image_name" => "140" "field_branch_parent" => Illuminate\Database\Eloquent\Collection {#1219 #items: [] #escapeWhenCastingToString: false } "field_weight" => "0" "field_book_parent" => Illuminate\Database\Eloquent\Collection {#1218 #items: array:1 [ 0 => App\Models\Book {#1220 #connection: "mysql" #table: "books" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:50 [ "id" => 4298 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1221 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1223 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1225 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1227 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1231 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1232 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1234 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1236 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1238 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1239 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1240 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1241 …2} "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1242 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1243 …2} "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1244 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1245 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1246 …2} "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1247 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #original: array:50 [ "id" => 4298 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1221 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1223 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1225 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1227 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1231 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1232 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1234 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1236 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1238 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1239 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1240 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1241 …2} "field_publication_number" => null "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1242 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1243 …2} "field_under_the_edition_degree" => null "field_cover_description" => null "field_publication_year" => "2019" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебник для учащихся 9 класса общеобразовательных школ" "field_allowed" => "Рекомендовано Министерством образования и науки Республики Казахстан" "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1291" "field_priority" => "4" "field_default_folder" => "/algebra_09/soltan-u19/" "field_isbn" => "978-601-317-424-2" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => null "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1244 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1245 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1246 …2} "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1247 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "edition_groups" => Illuminate\Database\Eloquent\Collection {#1248 #items: [] #escapeWhenCastingToString: false } "content" => Illuminate\Database\Eloquent\Collection {#1249 #items: array:1 [ 0 => App\Models\Element {#1250 #connection: "mysql" #table: "elements" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 1261033 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1251 …2} "book_page" => array:2 [ …2] "img" => array:1 [ …1] ] #original: array:6 [ "id" => 1261033 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1251 …2} "book_page" => array:2 [ …2] "img" => array:1 [ …1] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "next" => array:2 [ "refs" => "1097883" "type" => "book_page" ] "previous" => array:2 [ "refs" => "1097881" "type" => "book_page" ] "tasks" => Illuminate\Database\Eloquent\Collection {#1258 #items: array:8 [ 0 => App\Models\Task {#1259 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1108206 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "140" "field_page_end" => null "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik/1-478" "field_display_title" => "478" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1260 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1262 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1263 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1296 …2} "content" => Illuminate\Database\Eloquent\Collection {#1333 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1358 …2} "page" => array:2 [ …2] ] #original: array:24 [ "id" => 1108206 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "140" "field_page_end" => null "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik/1-478" "field_display_title" => "478" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1260 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1262 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1263 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1296 …2} "content" => Illuminate\Database\Eloquent\Collection {#1333 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1358 …2} "page" => array:2 [ …2] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 1 => App\Models\Task {#1359 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1108207 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "140" "field_page_end" => null "field_url" => "/9-klass/algebra/kokshetau-soltan-uchebnik/1-479" "field_display_title" => "479" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1360 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1362 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1363 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1396 …2} "content" => Illuminate\Database\Eloquent\Collection {#1461 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1486 …2} "page" => array:2 [ …2] ] #original: array:24 [ "id" => 1108207 "created_at" => "2026-04-10 13:58:26" …22 ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ …1] } 2 => App\Models\Task {#1515 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ …24] #original: array:24 [ …24] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ …1] } 3 => App\Models\Task {#1671 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ …24] #original: array:24 [ …24] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ …1] } 4 => App\Models\Task {#1827 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ …24] #original: array:24 [ …24] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ …1] } 5 => App\Models\Task {#1927 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ …24] #original: array:24 [ …24] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ …1] } 6 => App\Models\Task {#2083 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ …24] #original: array:24 [ …24] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ …1] } 7 => App\Models\Task {#2183 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: 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№485 (с. 140)
Условие. №485 (с. 140)
скриншот условия
485. Дана бесконечно убывающая геометрическая прогрессия ($c_n$),
сумма которой равна 8. Причем $c_n = \frac{1}{4}$ и $\frac{c_1 + c_2 + ... + c_{n-1}}{c_{n+1} + c_{n+2} + ...} = 30.$
Найдите номер члена прогрессии, равного $\frac{1}{4}$.
Решение. №485 (с. 140)
Решение 2 (rus). №485 (с. 140)
Пусть $c_1$ — первый член бесконечно убывающей геометрической прогрессии $(c_n)$, а $q$ — её знаменатель. По определению бесконечно убывающей геометрической прогрессии, $|q| < 1$.
Сумма бесконечно убывающей геометрической прогрессии вычисляется по формуле $S = \frac{c_1}{1-q}$.Из условия задачи известно, что сумма прогрессии равна 8, поэтому мы можем составить первое уравнение:
$\frac{c_1}{1-q} = 8$
Из этого уравнения выразим первый член прогрессии $c_1$:
$c_1 = 8(1-q)$ (1)
Рассмотрим второе условие, заданное в виде отношения сумм:
$\frac{c_1 + c_2 + ... + c_{n-1}}{c_{n+1} + c_{n+2} + ...} = 30$
Числитель этой дроби — это сумма первых $n-1$ членов геометрической прогрессии, $S_{n-1}$. Используем формулу суммы первых $k$ членов $S_k = \frac{c_1(1-q^k)}{1-q}$.Таким образом, числитель равен:
$S_{n-1} = \frac{c_1(1-q^{n-1})}{1-q}$
Поскольку мы знаем, что $\frac{c_1}{1-q} = 8$, мы можем подставить это значение в выражение для $S_{n-1}$:
$S_{n-1} = 8(1-q^{n-1})$
Знаменатель дроби, $c_{n+1} + c_{n+2} + ...$, представляет собой сумму бесконечно убывающей геометрической прогрессии, которая начинается с члена $c_{n+1}$ и имеет тот же знаменатель $q$. Сумма этого "остатка" прогрессии равна:
$S_{ост} = \frac{c_{n+1}}{1-q}$
Используя формулу $n$-го члена $c_k = c_1 q^{k-1}$, выразим $c_{n+1} = c_1 q^n$. Подставим это в формулу для суммы остатка:
$S_{ост} = \frac{c_1 q^n}{1-q} = q^n \cdot \frac{c_1}{1-q} = q^n \cdot 8 = 8q^n$
Теперь подставим полученные выражения для числителя и знаменателя в исходное уравнение с отношением:
$\frac{8(1-q^{n-1})}{8q^n} = 30$
Сократив на 8, получим:
$\frac{1-q^{n-1}}{q^n} = 30$
$1-q^{n-1} = 30q^n$
$1 = 30q^n + q^{n-1}$
Вынесем общий множитель $q^{n-1}$ за скобки:
$1 = q^{n-1}(30q+1)$
Отсюда можно выразить $q^{n-1}$:
$q^{n-1} = \frac{1}{30q+1}$ (2)
Теперь используем третье условие задачи: $c_n = \frac{1}{4}$.По формуле $n$-го члена: $c_n = c_1 q^{n-1}$.
$c_1 q^{n-1} = \frac{1}{4}$ (3)
Теперь у нас есть система из трех уравнений (1), (2) и (3). Подставим выражение для $c_1$ из (1) и для $q^{n-1}$ из (2) в уравнение (3):
$8(1-q) \cdot \frac{1}{30q+1} = \frac{1}{4}$
Решим полученное уравнение относительно $q$:
$\frac{8(1-q)}{30q+1} = \frac{1}{4}$
Используя свойство пропорции (произведение крайних членов равно произведению средних), получаем:
$4 \cdot 8(1-q) = 1 \cdot (30q+1)$
$32(1-q) = 30q+1$
$32 - 32q = 30q+1$
$31 = 62q$
$q = \frac{31}{62} = \frac{1}{2}$
Мы нашли знаменатель прогрессии. Теперь найдем первый член $c_1$, подставив значение $q$ в уравнение (1):
$c_1 = 8(1-q) = 8(1-\frac{1}{2}) = 8 \cdot \frac{1}{2} = 4$
Итак, мы определили параметры прогрессии: $c_1 = 4$ и $q = \frac{1}{2}$.Осталось найти номер члена прогрессии $n$, для которого $c_n = \frac{1}{4}$. Воспользуемся формулой $n$-го члена:
$c_n = c_1 q^{n-1}$
$\frac{1}{4} = 4 \cdot (\frac{1}{2})^{n-1}$
Разделим обе части уравнения на 4:
$\frac{1}{16} = (\frac{1}{2})^{n-1}$
Представим левую часть как степень числа $\frac{1}{2}$:
$\frac{1}{16} = \frac{1}{2^4} = (\frac{1}{2})^4$
Теперь уравнение имеет вид:
$(\frac{1}{2})^4 = (\frac{1}{2})^{n-1}$
Так как основания степеней равны, мы можем приравнять их показатели:
$4 = n-1$
$n = 5$
Таким образом, член прогрессии, равный $\frac{1}{4}$, имеет номер 5.
Ответ: 5
Другие задания:
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