## Algebra and Trigonometry 10th Edition

$-i\sqrt {15}, 15$
$\sqrt {-15}= \sqrt {15}i$ 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.