Question

What is the domain and range of `2x-4y=-8`?

Answer 1

Your function is a Linear Function. It can accept every real value of `x` so that the domain is from `-oo` to `+oo`.
The range of your function (possible values of `y`) is as well from `-oo` to `+oo`.

Graphically your function is represented by a straight line:
graph{(1/2)x+2 [-10, 10, -5, 5]}