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