## Precalculus (10th Edition)

$40320$
We know that $P(n,r)=\dfrac{n!}{(n-r)!}$ and $0!=1$. Hence, $P(8,8)=\dfrac{8!}{(8-8)!}=\dfrac{8\cdot7\cdot6\cdot5\cdot4\cdot3\cdot2\cdot1}{0!}=8\cdot7\cdot6\cdot5\cdot4\cdot3\cdot2\cdot1=40320$