# Homework Help: Inverse for cubic function

1. Aug 22, 2013

### tg43fly

1. The problem statement, all variables and given/known data

Find the inverse of f(x)=ln(x^3-3x^2+3x-1)

2. Relevant equations

n/a

3. The attempt at a solution

y=ln(x^3-3x^2+3x-1)
x=ln(y^3-y^2+3y-1)
e^x=(y^3-y^2+3y-1)

i looked around for inverse of cubic functions and i found a monster of a formula:
http://www.math.vanderbilt.edu/~schectex/courses/cubic/
i really hope i missed something to find the inverse

2. Aug 22, 2013

### D H

Staff Emeritus
You dropped a very important factor of three in going from y=ln(x^3-3x^2+3x-1) to x=ln(y^3-y^2+3y-1).

Those factors of three should suggest something. Hint:Look at Pascal's triangle.

3. Aug 22, 2013

### tg43fly

whoops
$$y=ln(x^3-3x^2+3x-1)$$
$$y=ln(x-1)^3$$
$$x=ln(y-1^3)^3$$
$$e^x=(y-1)^3$$
$$y=e^x/3+1$$
ty for the hint