(n+2)!=n!*(n+1)*(n+2)
(n+2)!=(n-1)!*n*(n+1)*(n+2)
[m]lim_{ n→ ∞ }\frac{(n+2)!\cdot (\frac{n!}{(n+2)!}+\frac{(n+2)!}{(n+2)!})}{(n+2)!\cdot (\frac{(n-1)!}{(n+2)!}+\frac{(n+2)!}{(n+2)!})}=lim_{ n→ ∞ }\frac{\frac{1}{ (n+1)\cdot (n+2)}+1}{\frac{1}{n\cdot (n+1)\cdot (n+2)}+1}=\frac{0+1}{0+1}=1[/m]