Question

 calcule
 a)4!.5!/7!
B)(n+2)!/n!

Answer 1

Olá, Eliana.

$a)\,\frac{4!.5!}{7!}=\frac{4!.5!}{7.6.5!}=\frac{4.3.2.1}{7.6}=\frac{4.6.1}{7.6}=\frac47\\\\ b)\,\frac{(n+2)!}{n!}=\frac{(n+2)(n+1)n!}{n!}=(n+2)(n+1)=n^2+n+2n+2=\\\\=n^2+3n+2$