## Introductory Algebra for College Students (7th Edition)

$r^6-4$
Using $(a+b)(a-b)=a^2-b^2$ or the special product of the sum and difference of like terms, the product of the given expression, $(r^3+2)(r^3-2) ,$ is \begin{array}{l}\require{cancel} r^3(r^3)-2(2) \\\\= r^6-4 .\end{array}