Answer
$-12\sqrt {14}$
Work Step by Step
Make the square roots positive by creating an imaginary number outside them. Then multiply the terms in the parentheses and turn $i^2$ into $-1$. Then simplify the radical.
$(3\sqrt {-7})(2\sqrt {-8})$
$(3i\sqrt {7})(2i\sqrt {8})$
$6i^2\sqrt {56}$
$-6\sqrt {56}$
$-12\sqrt {14}$
