Intermediate Algebra (6th Edition)

$-49xy^{2}$
We are given the expression $(-7xy)(7y)$. $(-7xy)\times(7y)=(-7\times7)\times(x)\times(y\times y)$ We can use the product rule to simplify the third term, which holds that $a^{m}\times a^{n}=a^{m+n}$. Therefore, $(-7\times7)\times(x)\times(y\times y)=-49\times x\times y^{1+1}=-49xy^{2}$