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Need help on this differential equation

  1. Sep 17, 2011 #1
    1. The problem statement, all variables and given/known data
    Well this is a physics problem, need find the potential function



    2. Relevant equations
    [itex]\Psi[/itex] =Axe-kx A and k are constants
    I need to find d2 [itex]\Psi[/itex]/dx2


    3. The attempt at a solution
    I thought u would just take the derivative two times
    but just d[itex]\Psi[/itex]/dx = Ae-kx-kAxe-kx
    Would i do something like this?
    http://tutorial.math.lamar.edu/Classes/DE/Linear.aspx
    thanks
     
  2. jcsd
  3. Sep 17, 2011 #2

    vela

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    What's the problem with just differentiating it again?
     
  4. Sep 17, 2011 #3
    i forgot how you do a differential equation, i have the solutions. I want to know how you do the dΨ/dx
    i thought it would just be dΨ/dx= -A/ke-kx Its been a long summer lol
     
  5. Sep 17, 2011 #4

    vela

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    You don't have a differential equation. You're simply differentiating a function twice.

    For this particular function, you need to use the product rule and chain rule, and you need to know how to differentiate a polynomial and an exponential.
     
  6. Sep 17, 2011 #5
    o ok thxs the wolfan alpha thing said it was when i typed it in. It also gave somthing different
     
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