Chapter 9 - Quadratic Functions and Equations - 9-3 Solving Quadratic Equations - Practice and Problem-Solving Exercises - Page 551: 8

x=±3

You add 9 to both sides. That gives you $x^{2}=9$ Then you square root both sides to get the final answer of $\sqrt x^{2}=\sqrt 9$ **** The root of 9 is 3 because 3 x 3 = 9 x=±3 The square root of any number always has two answers, therefore we can have positive or negative sign (±)