Предмет: Математика, автор: задрот12

в арифметической прогрессии y1=3,y70=333.найдите сумму 70 первых членов

Ответы

Автор ответа: xxxeol

РЕШЕНИЕ
Суммируем первое и последнее число и умножаем на половину таких пар.
S = (y1+y70)*(1+70)/2 = 336*35 = 11760 - ОТВЕТ

Автор ответа: сева14

формула суммы прогрессии

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