Предмет: Алгебра, автор: grubyy1999

Найти сумму первых восьми членов арифметической прогрессии (аn): в которой а1=6 и а7=26.

Ответы

Автор ответа: 4EJI0BEK

Вроде все правильно, S⁸ = 336

Сравни с ответами на задних страницах книги

Приложения:

grubyy1999: Почему мы прибавляем 78?

4EJI0BEK: Это а⁸, по формуле Sn = (a¹ + an)/2 × n

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