Results 1 to 4 of 4

Math Help - 1st order ODE

  1. #1
    Banned
    Joined
    Nov 2010
    Posts
    8

    Smile 1st order ODE

    Does anyone know how to solve dy/dx=(x-y)/(x+y), with initial condition y(1)=-2. I am looking for an explicit form solution.

    I get stuck when I separate the equations and have to the integrate 0dx but that doesnt make any sense

    Many thanks guys
    Last edited by mr fantastic; November 24th 2010 at 11:37 AM. Reason: Re-titled.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by MathsLion View Post
    Does anyone know how to solve dy/dx=(x-y)/(x+y), with initial condition y(1)=-2. I am looking for an explicit form solution.

    I get stuck when I separate the equations and have to the integrate 0dx but that doesnt make any sense

    Many thanks guys
    Substitute y = xv. You will have an exmaple in your class notes or textbook (homogenous differential equation).
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Banned
    Joined
    Nov 2010
    Posts
    8
    hi

    what do you mean by let y=xv

    where does v come into this? I am still confused
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by MathsLion View Post
    hi

    what do you mean by let y=xv

    where does v come into this? I am still confused
    You make the substitution y = xv in the differential equation.

    Please go to your class notes or textbook first and spend some time reviewing this type of equation (I have told you its name and told you the technique). Then, if you are still confused, ask for more help.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Re-writing higher order spatial derivatives as lower order system
    Posted in the Differential Equations Forum
    Replies: 11
    Last Post: July 27th 2010, 08:56 AM
  2. Replies: 1
    Last Post: October 27th 2009, 04:03 AM
  3. Replies: 2
    Last Post: February 23rd 2009, 05:54 AM
  4. Replies: 2
    Last Post: November 25th 2008, 09:29 PM
  5. Replies: 4
    Last Post: August 12th 2008, 04:46 AM

Search Tags


/mathhelpforum @mathhelpforum