The function f is such that f(x)=4x-1 find f^-1(x)

Let y=4x-1
The inverse is basically expressing x in terms of y.
y=4x-1  =>
y+1=4x
x=(y+1)/4
Since the inverse is still a function of x, we only have to interchange x and y
inverse of f(x) = f^-1(x) = (x+1)/4