Chapter 6 - Factoring, Solving Equations, and Problem Solving - 6.2 - Factoring the Difference of Two Squares - Problem Set 6.2 - Page 248: 36

$4x(1+3x)(1-3x)$

Factoring out the greatest common factor of 4x, the given expression, $ 4x-36x^3 ,$ is equivalent to \begin{array}{l}\require{cancel} 4x(1-9x^2) .\end{array} Using $a^2-b^2=(a+b)(a-b)$, the completely factored form of the expression above is \begin{array}{l}\require{cancel} 4x(1+3x)(1-3x) .\end{array}