What is the domain of f (x) = 5x

Any real number multiplied by - 5 and to which 4 is then added will give a real answer, So the function is defined for all real values of x.

(-infinity, + infinity)

Step-by-step explanation:

Even tho' f (x) = 5x has only one term, it's still classified as a polynomial. All polynomials are defined on all x: (-infinity, + infinity).