Answer
The domain of this function is $\text{all real numbers}$.
Work Step by Step
When this question asks for the domain of the function, it is asking for the values of x that can be legally substituted into the function. (For instance, in the function $\frac{3}{x}$, $x≠0$ because this would make the denominator of the fraction equal to 0, making the function at that value be undefined.)
In the case of the function $y=x^2+4$, we can substitute any value of $x$ into the function and still get a valid $y$ value.
Therefore, the domain of this function is $\text{all real numbers}$.
