Chapter 10 - Radical Expressions and Equations - 10-5 Graphing Square Root Functions - Practice and Problem-Solving Exercises - Page 629: 15

$x \geq 4$

You can not take the square root of a negative number. Thus, 3(x - 4) must be greater than or equal to 0. $3(x - 4) \geq 0$ We divide both sides by 3. Zero divided by anything is zero $x - 4 \geq 0$ We add 4 to both sides $x \geq 4$