Answer
$-i\sqrt {15}, 15$
Work Step by Step
$\sqrt {-15}= \sqrt {15}i$
Rewrite the expression in standard form.
Complex conjugate of the above expression is $-\sqrt {15} i$ as
the complex conjugate of a+bi is a-bi.
$-\sqrt {15}i * \sqrt {15}i= -i^2*15 = 1*15=15$
Multiply the number and its complex conjugate.
