1. Not finding help here? Sign up for a free 30min 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!

First Order Homogeneous Equation

  1. Sep 19, 2009 #1
    1. The problem statement, all variables and given/known data

    (4y4-9x2y2-144)dx - (5xy3)dy = 0


    2. Relevant equations
    substitute y = xv
    dy = dx v + dv x


    3. The attempt at a solution
    after substituting i got

    (4x4v4-9v2x4-14x4)dx - (5v3x4)dx.v + dv.x

    = (4v4-9v2-14)dx - 5v3(dx.v + dv.x) = 0
    = dx(4v4-9v2-14-5v4)+dv(-5v3x)= 0
    dx/x = (-5v3dv)/(v4-9v2-14)

    dx/x = ((2v)/(v2+2) - (7v)/(v2+7)) dv

    derive both sides

    ln(x) = ln(v2+2) - 3.5ln(v2+7)
    x + c = (v2+2) / (v2+7)3.5

    c = (((y/x)2+2) / ((y/x)2+7)3.5) - x


    what am i doing wrong?
     
  2. jcsd
  3. Sep 19, 2009 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    What reason do you have for thinking you are doing anything wrong?
     
  4. Sep 19, 2009 #3
    webworks (the online assignment thing my school uses) is telling me my answer is incorrect

    nvm i know where the mistake was made
     
    Last edited: Sep 19, 2009
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: First Order Homogeneous Equation
Loading...