Предмет: Алгебра, автор: 3693691

в арифметической прогрессии (An): a1=-21 a2=-16 a10=24 найдите a9

Ответы

Автор ответа: mrsstrekoza

считаем d.
d = a1 - a2 = 5
a9 = a10 - d = 19

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