Answer
$3a^{2}b\sqrt {10a}$
Work Step by Step
$\sqrt {90a^{5}b^{2}}$
=$\sqrt {90}\times\sqrt {a^{5}}\times\sqrt {b^{2}}$
=$\sqrt {9\times10}\times\sqrt {a^{4+1}}\times\sqrt {b^{2}}$
=$3\sqrt {10}\times a^{2}\sqrt {a}\times b$
=$3\times a^{2}\times b\times\sqrt {10}\times\sqrt {a}$
=$3a^{2}b\times\sqrt {10\times a}$
=$3a^{2}b\sqrt {10a}$
