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Why not separable (basic question)?

  1. Oct 31, 2009 #1
    In Example 1.5 of Differential Equations Demystified, the equation is y' +2xy = x, and the author claims this is not separable. Now, what am I missing. I try the following.

    1) dy/dx = x - 2xy
    2) dy/dx = x(1-2y)
    3) dy/(1-2y) = xdx

    I guess one of those is invalid but I just cannot identify which. Any help appreciated, thanks. This is part of an effort to brush up on ODE since it's been years since I took it and now I'm going for a Master's in Applied Math, need lots of help of this kind. Thanks
     
  2. jcsd
  3. Oct 31, 2009 #2

    Pengwuino

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    Hmm, are you sure that's the equation they gave? I don't see what's wrong with that.
     
  4. Oct 31, 2009 #3
    Yes, that's definitely the equation, and the author says
    "This equation is plainly not separable (try and convince yourself that this is so)."
     
    Last edited: Nov 1, 2009
  5. Oct 31, 2009 #4

    arildno

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    Dearly Missed

    You just separated it, disproving the author's claim.
     
  6. Nov 1, 2009 #5
    Author wrote me back saying that it was a mistake, so that is in fact a separable equation.
     
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