решите уравнение [tex]C n^{n-2} } +2n= 9[/tex] - №6836863

решите уравнение [tex]C n^{n-2} } +2n= 9[/tex]
- Предмет:
  Алгебра
- Автор:
  candycanelpxs
- 6 лет назад

Ответы 1

$C^{n-2}_n+2n=9\\ \frac{n!}{2!*(n-2)!}+2n=9\\ \frac{n^2-n}{2}+2n=9\\ n^2-n+4n=18\\ n^2+3n-18=0\\ D=9+4*1*18=9^2\\ n=\frac{-3+9}{2}=3 \\ n=\frac{-3-9}{2}=-6\\$ Ответ $n=3$
- Автор:
  anselmotssf
- 6 лет назад
- 0
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