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: Stubborn ODE

  1. Aug 27, 2005 #1

    I'm having trouble with this ODE:

    y' + 4xy - y^2 = 4x^2 - 7

    => y' = 4x^2 - 4xy + y^2 - 7
    = (2x - y)^2 - 7

    => x(dv/dx) + v = (2x-vx)^2 - 7
    = x^2(2-v)^2 - 7

    I assume this ODE is of the homogeneous type, so I've substituted v=y/x and gotten thus far, but, what's the next step?
  2. jcsd
  3. Aug 28, 2005 #2


    User Avatar
    Homework Helper

    Try to replace 2x-y by v and solve for v. .

  4. Aug 28, 2005 #3
    Hmm this looks exactly like one of the questions on my assignment. Don't know of you are from University of Melbourne but if you are then you are ignoring the explicit instruction that we're supposed to write up the solutions to the assignment independently.

    In any case if you are from the same uni as I am then a hint that I can give you w/o actually telling you how to do the question is to go back to the problem sheets. There is a question which requires the same technique.

    You are on the right track btw.
    Last edited: Aug 28, 2005
  5. Aug 28, 2005 #4
    Thanks, I've figured it out now! :tongue2:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook