## Introductory Algebra for College Students (7th Edition)

$5$
Using $\sqrt{x}\cdot\sqrt{y}=\sqrt{xy}$ or the product rule of radicals, the given expression, $\sqrt{5}\cdot\sqrt{5} ,$ is equivalent to \begin{array}{l}\require{cancel} \sqrt{5(5)} \\\\= \sqrt{(5)^2} \\\\= 5 .\end{array}