f(x) = 10x - 3
1. Replace f(x) with y
y = 10x - 3
2. Replace every x with y and replace every y with x:
x = 10y - 3
3. Solve for y:
add 3 to both sides:
x + 3 = 10y -3 + 3
x + 3 = 10y
Divide both sides by 10:
(x + 3)/10 = 10y/10
y = (x + 3)/10
4. Replace y with f−1(x)
f-1(x) = (x + 3)/10
f-1(17) = (17+3)/10 = 20/10 = 2
