Chapter 6 - Factoring, Solving Equations, and Problem Solving - 6.2 - Factoring the Difference of Two Squares - Problem Set 6.2 - Page 248: 17

$2(x+3y)(x-3y)$

Factoring out the greatest common factor of 2, the given expression, $ 2x^2-18y^2 ,$ is equivalent to \begin{array}{l}\require{cancel} 2(x^2-9y^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} 2(x+3y)(x-3y) .\end{array}