#### Answer

$[0,∞)$

#### Work Step by Step

We are given the function $f(x)=\sqrt x+3$.
The index of the radical is even, so we know that $\sqrt x$ will only be a real number if x is not negative.
Therefore, the domain of this function is all values of x such that $x\geq0$. This can be written as $[0,∞)$ in interval notation.