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Differentiate using chain rule

  1. Oct 25, 2007 #1
    Hi everyone,

    I'm new to this forum... I hope I've posted in the right section...

    How do I differentiate y=2e(2x+1) using the chain rule?

    I let u= (2x+1)

    so du/dx = 2

    but how do I differentiate y= 2eU ?

    thank you :)
  2. jcsd
  3. Oct 25, 2007 #2


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    Well, I see a multiplication and an exponentiation in that expression...
  4. Oct 25, 2007 #3
    Does it mean that I should use the chain rule again?

    and I get dy/du = 2eU

    so dy/dx = 4e(2x+1) ?
    Last edited: Oct 25, 2007
  5. Oct 25, 2007 #4


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    The fact that a problem uses the word "differentiate" does not mean it is a differential equation! I am moving this to the Calculus and Analysis forum.
  6. Oct 25, 2007 #5


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    First, do you mean
    [tex]y= 2e^{2x+1}[/itex]
    which in "ASCII" would be y= 2e^(2x+1). What you wrote, I would interpret as 2e times(2x+1) and there is no need for the chain rule!

    If you let u= 2x+1, then, yes, the chain rule says that the derivative of y= 2e^u, with respect to x, is dy/dx= 2e^u (du/dx). Since you have already determined that du/dx= 2, that is dy/dx= 2e^(2x+1) (2)= 4 e^(2x+1). There is no need for a second application of the chain rule.
  7. Oct 25, 2007 #6
    thank you very much :)
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