## Precalculus (6th Edition) Blitzer

The value of $_{9}{{P}_{5}}$ = $15,120$
We compare the provided expression with the standard form to get $n=9,r=5$. Put the values into the permutation formula: That is, \begin{align} & _{9}{{P}_{5}}=\frac{9!}{\left( 9-5 \right)!} \\ & =\frac{9!}{4!} \\ & =\frac{9\times 8\times 7\times 6\times 5\times 4!}{4!} \\ & =15,120 \end{align}