## Intermediate Algebra (6th Edition)

$27y^{5}$
We are given the expression $-3y\times-9y^{4}$. We can simplify by grouping like terms. $(-3\times-9)\times(y\times y^{4})$ Next, we can use the product rule, which holds that $a^{m}\times{a^{n}}=a^{m+n}$ (where a is a real number, and m and n are positive integers). $27\times(y^{1+4})=27y^{5}$