Answer
$5i\sqrt{2}$
Work Step by Step
Using the properties of radicals and that $i=\sqrt{-1}$, then the given expression, $
\sqrt{-50}
,$ is equivalent to
\begin{array}{l}\require{cancel}
\sqrt{-1}\cdot\sqrt{50}
\\\\=
i\cdot\sqrt{25\cdot2}
\\\\=
i\cdot\sqrt{(5)^2\cdot2}
\\\\=
i\cdot5\sqrt{2}
\\\\=
5i\sqrt{2}
.\end{array}