Question

simplifique a expressão Cx, 2 = 15

Answer 1

$C_{x,2}=15\Rightarrow C_{n,p}\left( \dfrac{n!}{p!(n-p)!}\right) \\\\\dfrac{x!}{2!(x-2)!}=15\\\\\\ \dfrac{x\cdot(x-1)\cdot(x-2)!}{2\cdot1!(x-2)!} =15\\\\\\ \dfrac{x\cdot(x-1)\cdot(\not x-2)!}{2\cdot1!(\not x-2)!} =15\\\\\\ \dfrac{x^2-x}{2}=15\\\\ x^2-x=2\cdot15\\ x^2-x-30=0\\\\\\ x_1=-5~(nao~convem)~~e~~x_2=6\\\\\\ \Large\boxed{\text{S}=\{6\}}$