1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Inverse for cubic function

  1. Aug 22, 2013 #1
    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. jcsd
  3. Aug 22, 2013 #2

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    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.
     
  4. Aug 22, 2013 #3
    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
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Loading...