#### Answer

Domain: $(-\infty, +\infty)$
Range: $\left\{3\right\}$
Refer to the image below for the graph.

#### Work Step by Step

$f(x)=3$
The y-intercept can be found by letting x=0.
Here,
$f(x)=3$
Hence, the y-intercept is 3, therefore we plot (0, 3)
However, it is a constant function, therefore we have to draw a vertical line.
The domain is $(-\infty, \infty)$ as the function will "work" for all real x-values.
(We can see the domain on the graph too. As for every x-value we will find a corresponding point on the graph.)
The range is ${3}$ as we will get only one real y-values after substituting all real x-values in the function.
(We can see the domain on the graph too. For only one y-value will we find a corresponding point on the graph.)