Chapter 9 - Section 9.1 - Solving Quadratic Equations by the Square Root Property - Exercise Set - Page 631: 8

$x=\pm3\sqrt{3}$

Since $x^2=a$ implies $x=\pm\sqrt{a}$ (the Square Root Property), then the solutions of the given equation, $ x^2=27 ,$ are \begin{array}{l}\require{cancel} x=\pm\sqrt{27} \\\\ x=\pm\sqrt{9\cdot3} \\\\ x=\pm\sqrt{(3)^2\cdot3} \\\\ x=\pm3\sqrt{3} .\end{array}