Answer
$\left\{-5, 5\right\}$
Work Step by Step
Add $125$ to both sides:
$5x^2=125$
Divide $5$ on both sides to obtain:
$x^2=25$
Take the square root of both sides:
$x=\pm \sqrt{25}
\\x=\pm \sqrt{5^2}
\\x=\pm 5$
Thus, the solution set of the given equation is $\left\{-5, 5\right\}$.
