Answer
$-2\sqrt 5 i, 20$
Work Step by Step
$\sqrt {-20}= 2\sqrt 5i$
Rewrite the expression in standard form.
Complex conjugate of the above expression is $-2\sqrt 5 i$ as
the complex conjugate of a+bi is a-bi.
$-2\sqrt 5 i * 2\sqrt 5 i = -4i^2*5 = 4*5=20$
Multiply the number and its complex conjugate.
