## College Algebra (10th Edition)

$P(4,4)=24$
Use the permutation formula to obtain: $P(n,r)=\frac{n!}{(n-r)!}$ $0!=1$ $P(4,4)=\frac{4!}{(4-4)!}=\frac{4!}{0!}=\frac{4\cdot3\cdot2\cdot1}{1}=24$ Or $P(4,4)=4\cdot3\cdot2\cdot1=24$ $P(4,4)=24$