Answer
$\left\{-11, 11\right\}$
Work Step by Step
RECALL:
If $x^2=a$, then taking the square root of both sides gives $x = \pm \sqrt{a}$.
Take the square root of both sides of the given equation to obtain:
$\sqrt{x^2}=\pm \sqrt{121}
\\x =\pm \sqrt{11^2}
\\x=\pm 11$
Thus, the solution set is $\left\{-11, 11\right\}$.
