## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$\dfrac{1}{25}-36x^8$
Using $(a+b)(a-b)=a^2-b^2$ or the product of the sum and difference of like terms, the given expression, $\left( \dfrac{1}{5}-6x^4 \right)\left( \dfrac{1}{5}+6x^4 \right)$, is equivalent to \begin{array}{l}\require{cancel} \left( \dfrac{1}{5} \right)^2-(6x^4)^2 \\\\= \dfrac{1}{25}-36x^8 .\end{array}