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

$x(4+9x)(4-9x)$
Factoring the $GCF= x$, the given expression, $16x-81x^3 ,$ is equivalent to \begin{array}{l} x(16-81x^2) .\end{array} Using $x^2-y^2=(x+y)(x-y)$ or the factoring of the difference of 2 squares, then the factored form of the expression, $x(16-81x^2) ,$ is \begin{array}{l} x(4+9x)(4-9x) .\end{array}