Question

What is the domain and range of `l(x) = 5x-4`?

Answer 1

Domain: all Real `x`;
Range: all Real `l`

Explanation:

Your function is a Linear Function that can be represented graphically by an infinite straight line.

The function can accept any value of `x` and gives, as output, any value of `l`.
The domain will then be all the Real `x` while the range will be all the Real `l`.

Graphically your function gives a line like this one:
graph{5x-4 [-10, 10, -5, 5]}