## Precalculus (6th Edition)

$10i\sqrt5$
Factor the radicand so that one factor is a perfect square then simplify to obtain: $=\sqrt{100(-5)} \\=\sqrt{10^2(-5)} \\=10\sqrt{-5}$ Factor out $-1$ in the radicand to obtain: $=10\sqrt{-1(5)}$ Since $\sqrt{-1} = i$, bring out the square root of $-1$, which is $i$, to obtain: $=10i\sqrt5$