Chapter 9 - Solving Quadratic Equations - 9.3 - Solving Quadratic Equations Using Square Roots - Exercises - Page 501: 12

$x=9$ and $x=-9$

The given equation is $\Rightarrow x^2-55=26$ Add $55$ to each side. $\Rightarrow x^2-55+55=26+55$ Simplify. $\Rightarrow x^2=81$ Take the square root of each side. $\Rightarrow x=\pm\sqrt {81}$ Simplify. $\Rightarrow x=\pm9$ Hence, the solutions are $x=9$ and $x=-9$.