Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$P(7,2) = 42$
Use the formmula $P=\dfrac{n!}{(n-r)!}$ to obtain: $\require{cancel} P(7,2) \\=\dfrac{7!}{(7-2)!} \\=\dfrac{7\times6\times5!}{5!} \\=\dfrac{7\times6\times\cancel{5!}}{\cancel{5!}} \\=7\times6 \\=42$