Question

(n+1)!/(n-1)!=6(n-1)

Answer 1

$\frac{(n+1)!}{(n-1)!}=6(n-1)\\ \\ \frac{(n+1)n.(n-1)!}{(n-1)!}=6(n-1)\\ \\ n(n+1)=6(n-1)\\ \\ n^2+n=6n-6\\ \\ n^2-5n+6=0\\ \\ n=2 \ ou \ n=3$