## Precalculus (6th Edition) Blitzer

$[3, +\infty)$
The radicand (expression inside a radical sign) of a square root cannot be negative as its root is an imaginary number. This means that: (1) The radicand of the first radical, which is $x-3$, must be greater than or equal to 0. Thus, $x$ can be any real number greater than or equal to $3$ (2) The radicand of the second radical, which is $x+4$, must be grater than or equal to 0. Thus, $x$ can be any real number greater than or equal to $-4$. Based on (1) and (2) above, the restrictions to the value of $x$ are: (1) $x \ge 3$; and (2) $x\ge -4$ Both of the restrictions above must be satisfied. Thus, the value of $x$ must be greater than or equal to $3$. Therefore, the domain of the given function is $[3, +\infty)$.