f(x)^-1 is asking for the inverse function of f(x).
The first step to finding the inverse is:
1) change f(x) to y
2) switch x and y
3) resolve the equation for y =
f(x) = 4x - 3
y = 4x - 3
x = 4y - 3
add 3 to both sides
x + 3 = 4y
divide both sides by 4
(x + 3)/4 = y
y = (x + 3)/4