Answer
$8\sqrt 7$
Work Step by Step
To simplify the expression, we will first simplify the term within the square root:
$4\sqrt {28}$
=$4\sqrt {4\times7}$
=$4(\sqrt 4\times\sqrt 7)$
=$4(\sqrt {2^{2}}\times\sqrt 7)$
=$4(2\times\sqrt 7)$
=$8\sqrt 7$
