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: Help Solving a differential equation

  1. Feb 1, 2006 #1
    Hello, i was wondering if someone can help me along with solving this differential equation.


    I believe you use substitution. Right now I am setting my substitution to
    v=(x+2y), but then when i follow through with my work, it doesn't simplify down to a seperable or first order linear equation. Am I doing something wrong?

    Last edited: Feb 1, 2006
  2. jcsd
  3. Feb 1, 2006 #2
    try this should make a nice linear in terms of x

    divide the left side by y

    then divide 1 by y' and you should end up with a linear in terms of x
  4. Feb 2, 2006 #3
    Rewrite this in the form M(x,y)dx + N(x,y)dy = 0. Then, check if this is an exact differential equation. If not, can you find an integrating factor to make it exact?

    I don't think substitution works here. It's just not separable.
  5. Feb 2, 2006 #4


    User Avatar
    Science Advisor

    This is NOT an exact equation either.

    I like Valhalla's suggestion. You can rewrite it as

    y(dx/dy)= x+ 2y which is a LINEAR equation for x as a function of y. If you really need y as a function of x, invert the function.
  6. Feb 2, 2006 #5
    I didn't say it was exact... I said he should check if it was exact. :smile:

    It's easy enough to make it exact with an integrating factor though.

    There is more than one way to skin a cat...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook