Question

Calcule
n!+(n-1)! / (n+1)! =1/8

Answer 1

n!+(n-1)! / (n+1)! =1/8
$\frac{n!+(n-1)!}{(n+1)!}= \frac{1}{8}$
$\frac{n(n-1)!+(n-1)!}{(n+1)n(n-1)!} = \frac{1}{8}$
$\frac{(n-1)!(n+1)}{(n+1)n(n-1)!} = \frac{1}{8}$
$\frac{1}{n} = \frac{1}{8}$
n=8