Chapter 10 - Radical Expressions and Equations - 10-5 Graphing Square Root Functions - Practice and Problem-Solving Exercises - Page 629: 14

$ x \geq -3 $

You can not take the square root of a negative number. Therefore, $3x + 9$ must be greater than or equal to 0. $3x + 9 \geq 0$ We subtract 9 from both sides $3x \geq -9$ We divide both sides by 3. $ x \geq -3 $