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

$(a^2b^2+4)(ab+2)(ab-2)$
Using $a^2-b^2=(a+b)(a-b)$ or the factoring of the difference of $2$ squares, then the factored form of the given expression, $a^4b^4-16$, is \begin{array}{l} (a^2b^2+4)(a^2b^2-4) \\\\= (a^2b^2+4)(ab+2)(ab-2) .\end{array}