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

$7i$
Using the properties of radicals and that $i=\sqrt{-1}$, then the given expression, $\sqrt{-49} ,$ is equivalent to \begin{array}{l}\require{cancel} \sqrt{-1}\cdot\sqrt{49} \\\\= i\cdot\sqrt{(7)^2} \\\\= i\cdot7 \\\\= 7i .\end{array}