## Introductory Algebra for College Students (7th Edition)

$y=\pm9$
Since $x^2=a$ implies $x=\pm\sqrt{a}$ (the Square Root Property), then the solutions of the given equation, $y^2=81 ,$ are \begin{array}{l}\require{cancel} y=\pm\sqrt{81} \\\\ y=\pm\sqrt{(9)^2} \\\\ y=\pm9 .\end{array}