Chapter 2 - Equations, Inequalities, and Problem Solving - 2.4 Applications with Percent - 2.4 Exercise Set - Page 111: 92

$9x^2$

$\bf{\text{Solution Outline:}}$ Use the definition of exponents to simplify the given expression, $ (-3x)^2 .$ $\bf{\text{Solution Details:}}$ With an exponent of $2$, mutliply the given expression to itself. Hence, \begin{array}{l}\require{cancel} (-3x)^2 \\\\= (-3x)(-3x) \\\\= 9x^2 .\end{array}