## Algebra 1: Common Core (15th Edition)

$n^{C}_{n-1}=\frac{n!}{(n-1)!(n-(n-1))!}$ $n^{C}_{n-1}=\frac{n!}{(n-1)!=\frac{n!}{(n-1)!}}$ By the definition of factorial we can write it as: n!=n.(n-1)! $n^{C}_{n-1}=\frac{n.(n-1)!}{(n-1)!}$