## Elementary Algebra

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