Chapter 8 - Section 8.4 - Equations Quadratic in Form - Exercise Set - Page 635: 3

{$\pm \sqrt 2, \pm 3$}

Since, $u^2-11u+18=0$ Factorize the expression as follows: $(u-2)(u-9)=0$ or, $u=${$2,9$} Replace $u$ with $x^2$, we have $x^2=2$ and $x^2=9$ This implies that $x=\pm \sqrt 2, \pm 3$ Hence, our solution set is $x=${$\pm \sqrt 2, \pm 3$}