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: Strange way of solving a linear 2nd order DE

  1. Nov 16, 2012 #1
    1. The problem statement, all variables and given/known data
    I was given a DE of the form: [tex]\Phi^{''}+(6/\eta)\Phi^{'}=0[/tex] where the next step was given as [tex]\Phi^{'} \propto \eta^{-6}[/tex] where the answer came out to be [tex]\Phi \propto \eta^{-5} + constant[/tex]

    3. The attempt at a solution
    My attempt was to set [tex]\Phi^{'}=x[/tex] where I would then get [tex]x^{'}=-(6/\eta)x[/tex] and then solve for a seperable DE, but my answer was incorrect. Any help would be appreciated, thanks guys.

    Any help would be appreciated, thanks guys.
  2. jcsd
  3. Nov 16, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    To clarify, η is the independent variable, and differentiation is wrt that? If so [tex]dx/x=-6d\eta/\eta[/tex] yes? Isn't it straightforward from there?
  4. Nov 16, 2012 #3
    About 5 minutes after posting this I figured it out. :/ Thanks for replying though, I appreciate it, that's exactly what I got. Cheers!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook