Answer
$x=11$ or $x=-11$
Work Step by Step
$ x^{2}=121\qquad$... use the principle of square roots:
For any real number $k$ , if $x^{2}=k$ , then
$x=\sqrt{k}$ or $x=-\sqrt{k}$
$ x=\pm 11\qquad$... the symbol $\pm$ indicates two solutions.
$x=11$ or $x=-11$
