Question

Cine mă poate ajuta? Dau 20 pcte

Answer 1

Formula combinarilor: $\frac{n!}{k!*(n-k)!}$

=> $\frac{11!}{9!*(11-9)!} =\frac{11!}{9!*2!} =\frac{1*2*..*9*10*11}{1*2*..*9 * 2} =\frac{10*11}{2} =55$

$\frac{11!}{2!*(11-2)!} =\frac{11!}{2!*9!} =\frac{1*2*..*9*10*11}{1*2*..*9 * 2} =\frac{10*11}{2} =55$

=> 55-55=0