Introductory Algebra for College Students (7th Edition)

$x\sqrt{17}$
Getting the perfect factors and then extracting its root, the simplified form of the given expression, $\sqrt{17x^2} ,$ is \begin{array}{l}\require{cancel} \sqrt{x^2\cdot17} \\\\= \sqrt{(x)^2\cdot17} \\\\= x\sqrt{17} .\end{array}