Step-by-step explanation:
If you are talking about an inverse function f-1(x) of the function f(x), you must remember that, by definition,
f(f-1(x)) = x
So given f(x) = x/4 if I apply an arbitrary K which is equal to f-1(x), then
f(K) = x
K/4 = x
K = 4x
But I want to recover f-1(x), so replace it back.
f-1(x) = 4x
Done