#### Answer

$x=\pm15$

#### Work Step by Step

$\bf{\text{Solution Outline:}}$
To solve the given equation, $
x^2=225
,$ take the square root of both sides (Square Root Property). Then simplify the resulting radical.
$\bf{\text{Solution Details:}}$
Taking the square root of both sides (Square Root Property), the equation above is equivalent to
\begin{array}{l}\require{cancel}
x=\pm\sqrt{225}
.\end{array}
Simplifying the radical results to
\begin{array}{l}\require{cancel}
x=\pm\sqrt{(15)^2}
\\\\
x=\pm15
.\end{array}