Answer
$-12-12i\sqrt 7\approx-12-31.749i$
Work Step by Step
$-4(3+\sqrt {-63})$
=$-12-4\sqrt {-9\times7}$
=$-12-4(\sqrt {-1\times9\times7})$
=$-12-4(\sqrt {-1}\times\sqrt 9\times\sqrt 7)$
=$-12-4(i\times3\times\sqrt 7)$
=$-12-12i\sqrt 7\approx-12-31.749i$
