## Intermediate Algebra (12th Edition)

$36r^4-1$
Using $(a+b)(a-b)=a^2-b^2$ or the product of the sum and difference of like terms, the product of the given expression, $(6r^2-1)(6r^2+1) ,$ is \begin{array}{l}\require{cancel} (6r^2)^2-(1)^2 \\\\= 36r^4-1 .\end{array}