Предмет: Алгебра, автор: LOLYOU1337

в арифметической прогрессии y; 3y+5; 5y+10;... сумма первых восьми членов равна 396.Найдите y.

Ответы

Автор ответа: vanya190598
0
Разность прогрессии d=(3y+5)-y d=2y+5 Сумма 8-ми первых членов выражается формулой S=(((2*y+d(8-1))8)/2 Ответ: y=4
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