Срочно!!!a1=-17d=6Найти S9-? - №31564894

Срочно!!!
a1=-17
d=6
Найти S9-?
- Предмет:
  Алгебра
- Автор:
  barbies9ye
- 5 лет назад

Ответы 1

Sₙ = ( ( 2a₁+d(n-1) ) /2 )*n
S₉ = ((-17 *2 + 6(9-1)) / 2 )*9 = 63
- Автор:
  hammer
- 5 лет назад
- 0
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