Question

Aranjamente de x luate cate 2 = 12
x = ?

Answer 1

$A_{n}^k= \frac{n!}{(n-k)!},deci. A_{x}^2= \frac{x!}{(x-2)!}=x*(x-1)=12$ deci avem de rezolvat in N ecuatia: x(x-1)=4*3, fiind x-1 si x doua numere consecutive ⇒x=4