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I Need help with a derivative solution

  1. Aug 28, 2016 #1
    Hello.
    We have the derivative of a function: d F(x)/dx. If we substitute x = au, how can I show that d F(x)/dx = (1/a) (dF/du) ?
     
  2. jcsd
  3. Aug 28, 2016 #2

    QuantumQuest

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    When you do a substitution, you take the derivatives of both sides (hint: take into account what is constant and what is not). If you do this, you'll immediately come to what you need to show.
     
  4. Aug 28, 2016 #3
    Thanks for the answer, did it and got:
    (dF/da) (dF/du) = (dF/da) u + (dF/du) a = (dF/du) a, since a is a constant. What am I missing here?
     
  5. Aug 28, 2016 #4

    QuantumQuest

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    As I previously said, note that ##dx = a\cdot du##.
     
  6. Aug 28, 2016 #5
    Thanks, got it now.
     
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