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: How to solve this simple polynomial?

  1. Nov 28, 2011 #1
    xy'^2 + yy' = 0 where y' = dy/dx

    The answer is C1 = y and C2 = xy but I get this:

    y'(xy' + y) = 0 where y' = 0 and thus y = C1

    For the other solution:
    xy' + y = 0
    y' = -y/x
    y = -y ln x + C2
    C2 = y + y ln x

    Full question is here: http://www.cramster.com/solution/solution/640396
  2. jcsd
  3. Nov 28, 2011 #2


    User Avatar
    Homework Helper

    You can't take the antiderivative of that expression because y is a function of x but you've treated y as a constant.

    Try get the x and dx on one side, and the y and dy on the other, then integrate.
  4. Nov 28, 2011 #3
    Ah, I see my mistake now. Thanks!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook