## Intermediate Algebra (6th Edition)

$9b^2-36y^2$
Using $(a+b)(a-b)=a^2-b^2$ or the product of the sum and difference of like terms, the expression, $(3b-6y)(3b+6y)$, is equivalent to \begin{array}{l} (3b)^2-(6y)^2 \\\\= 9b^2-36y^2 .\end{array}