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: Help solving Homo ODE

  1. Nov 13, 2011 #1
    Hi, need help solving a first order homogeneous ODE.

    y'(x)-(a/x)y = b/(x(1+x)^2) Here a and b are some constants.

    Need to solve this for y.

    My attempts so far have been to use

    img1.gif

    But this means solving ∫ x^(-a)/(x(1+x)^2) dx which has solutions in terms of Gauss hyper-geometric functions,

    http://en.wikipedia.org/wiki/Hypergeometric_function" [Broken]

    Which lead me to believe i'm going wrong somewhere....

    Sorry for the maths format, i'm new to here and don't know how to insert LaTeX.

    Thanks
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Nov 13, 2011 #2
    What, he didn't give you an easy one huh? But isn't the integrating factor x^(-a) so that you get:

    [tex]d(yx^{-a})=\frac{b}{x^{1+a}(1-x)^2}[/tex]

    Now suppose all you had to do was:

    [tex]\int \frac{b}{x^{1+a}(1-x)^2}dx[/tex]

    Could you use parts say, one, two, three, four times, look at what's happening to the sequence, then come up with a general (infinite-term) expression for the solution that when you checked out the power-series expression for the Hypergeometric series solution reported by Mathematica, the series you get looks like it?
     
  4. Nov 14, 2011 #3
    thanks for the response Jackmell,

    Am currently working on it, though keep making maths errors which are slowing me down.

    I agree it would be a good idea to compare, thanks for the tip.

    The problem is part of a project, so yea the problems not meant to be easy.
    demoralising thing though is that i'm not sure i was supposed to take this long with it!

    Konig
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook