Chapter 6 - Factoring, Solving Equations, and Problem Solving - 6.2 - Factoring the Difference of Two Squares - Problem Set 6.2 - Page 248: 26

$3(5+x)(5-x)$

Factoring out the greatest common factor of 3, the given expression, $ 75-3x^2 ,$ is equivalent to \begin{array}{l}\require{cancel} 3(25-x^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} 3(5+x)(5-x) .\end{array}