Answer
$4i\sqrt 2$
Work Step by Step
Step 1: $\sqrt {-32}$
Step 2: $\sqrt {-1}\times\sqrt {32}$
Step 3: $\sqrt {-1}\times\sqrt 2\times\sqrt {16}$
Step 4: As $\sqrt {-1}=i$, the expression becomes $i\times\sqrt 2\times\sqrt {16}$.
Step 5: $i\times\sqrt 2\times\sqrt {16}=i\times\sqrt 2\times4$
Step 6: $i\times\sqrt 2\times4=4i\sqrt 2$