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!

Help me finding inverse function

  1. Oct 3, 2007 #1
    What is the inverse of this function [tex]f(x) = x^3 + 2x[/tex]?


    [tex]f(x) = x^3 + 2x[/tex]

    [tex]y = x^3 + 2x[/tex]

    interchange [tex]x \Leftrightarrow y[/tex]

    [tex]x = y^3 + 2y[/tex]

    and it's a dead end to me ...
  2. jcsd
  3. Oct 3, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    That will not get you where you need to be. Rather then simply interchanging x and y, you need to chang your expression for f(x) as F(y). A simple example:

    f(x)= 3x + 5

    y = 3x + 5

    y - 5 = 3x

    y/3 - 5/3 = x

    x = y/3 - 5/3

    so now you have x = F(y)
  4. Oct 3, 2007 #3


    User Avatar
    Science Advisor

    What you need to do is solve the equation x3+ 2x= y for x. Thats solving a fairly general cubic equation. Do you have any reason to think that the inverse can be written in a simple form?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Help finding inverse Date
Need help finding determinant Nov 12, 2017
Help with finding inverse Sep 11, 2011
Need help finding inverse transformation for Jacobian Mar 4, 2010
Finding Inverse (confused) help Asap Feb 15, 2007