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

$7(p^2+q^2)(p+q)(p-q)$
Factoring the $GCF= 7$, then the given expression, $7p^4-7q^4$ is equivalent to \begin{array}{l} 7(p^4-q^4) .\end{array} Using $a^2-b^2=(a+b)(a-b)$ or the factoring of the difference of $2$ squares, then the complete factored form of the expression above is \begin{array}{l} 7(p^2+q^2)(p^2-q^2) \\\\= 7(p^2+q^2)(p+q)(p-q) .\end{array}