Question

What is the domain and range of `f(x)=2x+4`?

Answer 1

I found:
Domain: all real `x`;
Range: all real `y`.

Explanation:

Your function is a Linear Function represented graphically by a straight line passing through `x=0, y=4` and with slope equal to `2`.
It can accept all real `x` and produces, as output, all real `y`.
graph{2x+4 [-10, 10, -5, 5]}