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: Ordinary differential equation:

  1. Nov 14, 2007 #1
    1. The problem statement, all variables and given/known data
    Obtain the general solution:
    [tex](1 - x)y' = y^2[/tex]

    2. Relevant equations

    3. The attempt at a solution
    [tex](1 - x)\frac{dy}{dx} = y^2[/tex]

    [tex](1 - x)dy = y^2dx[/tex]

    [tex]\frac{dy}{y^2} = \frac{dx}{(1-x)}[/tex]
    integrating both sides:

    i used ln on the constant at the right side
    [tex]-\frac{1}{y} = \ln(1 - x) + \ln{c}[/tex]

    so my answer is:
    [tex]-1 = y\ln{(c(1 - x))}[/tex]

    the answer seems to be different at the back of my book w/c is
    [tex] 1 = y\ln{(c(1 - x))}[/tex] <<< no negative as before

    can you tell me what's wrong with my soln?
  2. jcsd
  3. Nov 14, 2007 #2


    User Avatar
    Science Advisor

    Here is the problem. What do you get if you differentiate ln(1-x)? (Don't forget to use the chain rule!)

  4. Nov 14, 2007 #3
    oh yeah! forgot about that thanks alot :D
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook