#### Answer

$-5i\sqrt{6}$

#### Work Step by Step

Using the properties of radicals and that $i=\sqrt{-1}$, then the given expression, $
-\sqrt{-150}
,$ is equivalent to
\begin{array}{l}\require{cancel}
-\sqrt{-1}\cdot\sqrt{150}
\\\\=
-i\cdot\sqrt{25\cdot6}
\\\\=
-i\cdot\sqrt{(5)^2\cdot6}
\\\\=
-i\cdot5\sqrt{6}
\\\\=
-5i\sqrt{6}
.\end{array}