Answer
$-2\sqrt 3$
Work Step by Step
$\sqrt -2 \times \sqrt -6=\sqrt (4\times-1\times-1\times3)=\sqrt 4\times\sqrt -1\times\sqrt -1\times\sqrt 3=2\times i\times i\times\sqrt 3=2\times i^{2}\times\sqrt 3=-2\sqrt 3$
We know that $\sqrt -1=i$ and that $i^{2}=-1$.
