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Homework Help: Differential Equation Method Question

  1. Mar 3, 2010 #1
    dy/dx = (y-x)/(y+x)

    I am suppose to solve this equation using substitution, but isn't it possible to solve this equation an easier way since it is an exact equation?

    (y+x)dy - (y-x)dx = 0
     
  2. jcsd
  3. Mar 3, 2010 #2

    Gib Z

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    Homework Helper

    It's not an exact ODE. The form is [tex]P(x,y)dy + Q(x,y) dx = 0[/tex] for exact ODE's, you didn't bring the negative factor in.
     
  4. Mar 3, 2010 #3
    [tex]\frac{dy}{dx}=\frac{y-x}{y+x}=\frac{y}{y+x}-\frac{x}{y+x}[/tex]

    Use the substitution [tex]v=x+y[/tex].
     
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