Question

Cn,2 = 6


qual é a resposta

Answer 1

$\dfrac{n!}{2!(n-2)!} =6\\\\ \dfrac{n\cdot(n-1)\cdot(\not n-2)!}{2!(\not n-2)!}=6\\\\ n\cdot(n-1)=6\cdot2\\ n^2-n=12\\ n^2-n-12=0\\\\\\ n_1=-3~~\notin~~\mathbb{N}\\ n_2=4\\\\\\ \huge\boxed{\boxed{\text{S}=\{4\}}}$