Question

Помогите!!Срочно!!! (n-3)!/(n+1)!

Answer 1

$\frac{(n-3)!}{(n+1)!}=\frac{1\cdot2\cdot3\cdot\ldots\cdot(n-3)}{1\cdot2\cdot3\cdot\ldots\cdot(n-3)\cdot(n-2)\cdot(n-1)\cdot n\cdot(n+1)}=\frac1{(n-2)(n-1)n(n+1)}=\\=\frac1{(n^2-1)(n^2-2n)}=\frac1{n^4-2n^3-n^2+2n}$