Answer
$-3\sqrt 7$
Work Step by Step
You are given $\sqrt {28}$ $-5\sqrt 7$.
factor out a perfect square:$\sqrt {4{\times}7}$ $-5\sqrt 7$
multiplication property:$(\sqrt 4)$$(\sqrt 7)$$-5\sqrt 7$
simplify:$2\sqrt 7$$-5\sqrt 7$
Distributive property: $\sqrt 7(2-5)$
=$-3\sqrt 7$
