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

We know that: $_nC_r =\frac{_nP_r}{r!} = \frac{n!}{(n-r)!r!}$ $_nC_1 = \frac{n!}{(n-1)!1!}$ $\frac{ n*(n-1)!}{(n-1)!}= n$ So, it is always true