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Homework Help: Differential equation

  1. Jul 8, 2010 #1
    1. The problem statement, all variables and given/known data

    Find the general equation of differential equation dy/dx=y+x

    2. Relevant equations



    3. The attempt at a solution

    I don see a way to separate the variables. What substitution should i use?
     
  2. jcsd
  3. Jul 8, 2010 #2

    Office_Shredder

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    I only see three possible choices for a function in your equation: x, y, or x+y
     
  4. Jul 8, 2010 #3
    sorry but i don get what u meant
     
  5. Jul 8, 2010 #4

    Dick

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    I think Office_Shredder means you should look at the equation and take a guess at what might be a good substitution. What might work?
     
  6. Jul 8, 2010 #5

    hunt_mat

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    Failing that, you could try an integrating factor of e^{-x}
     
  7. Jul 8, 2010 #6

    HallsofIvy

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    You said you were looking for a substitution! It wouldn't do much good to let u= x or u= y, would it? So what if u= x+ y?
     
  8. Jul 8, 2010 #7

    LCKurtz

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    Substitution?? Have you studied linear equations or constant coefficient equations yet?
     
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