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Homework Help: Can't remember how to differentiate this

  1. Aug 21, 2007 #1
    for my Schrodinger equation I need the second derivative of this: Axe^(-x^2/ L^2)
    I think that I am missing some chain rule or something.

    The solutions say: ( 4Ax^3-6AxL^2)(1/L^4)e^(-x^2/ L^2)

    I only got -2Axe^(-x^2/L^2) for the 1st deriv. and 4Axe^(-x^2/L^2) and I still can't figure out what I'm missing even by looking at the solutions.
  2. jcsd
  3. Aug 21, 2007 #2


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    I think you are missing both the product rule and the chain rule. I'm not even sure what rule you are using. Warm up by taking the derivative of x*exp(-x^2). You should get exp(-x^2)-2*x^2*exp(-x^2). I think you may need to crack a first year calc text before dealing with the SE.
  4. Aug 21, 2007 #3
    Your first derivative is immediately wrong because you didn't use the product rule (but you also forgot chain rule).
  5. Aug 29, 2007 #4
    Thank you, your were both very right. I had immediately missed the product rule. Thanks for the help. :redface:
    Last edited: Aug 29, 2007
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