Question

Simplifique:assunto:número binominal

Answer 1

$\frac{ \left(\begin{array}{ccc}x\\5\end{array}\right) }{ \left(\begin{array}{ccc}x\\4\end{array}\right)}=\frac{\frac{x!}{(x-5)!5!}}{ \frac{x!}{(x-4)!4!}}= \\ \\ \\ \frac{x!}{(x-5)!5!}.\frac{(x-4)!4!}{x!}=\frac{(x-4).(x-5)!}{5(x-5)!}=\frac{x-4}{5}$