Step-by-step explanation: f(x) =3 means that Y is 3 for every value of X, as there's no X affected in the formula, so it will have that value always.
As there are also no restrictions, like 1/X or logX then you know that every value of X is possible to be replaced in f(x) fórmula [if there were any X in the formula, which is not the case]
