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Homework Help: Differentiate the exponential function

  1. May 9, 2005 #1

    I am having a bit of trouble, i am getting ready for an exam, one the questions i have asks
    "given the curve y = e^x, draw tangents to esitmate the gradients of the curve when
    a)x=0, b)x=1, c)x=-1,
    Now i know the answers are:
    a) 1 b) 7.39 c)0.05
    However the toruble i am having is understanding hwo to get to those points. For the first i got to this:
    x= 0
    dy/dx|x=0 =0e^(0-1), but then where do i go to get to the point where the answer become 1? Could someone help me with the others, i am having a large amoutn of difficulty to get this to click in my head, if anyone could help me out i would be very apreciable.

  2. jcsd
  3. May 9, 2005 #2

    You've either been studying way too hard or not nearly hard enough!

    The derivative of e^x isn't xe^(x-1). You're thyinking of the derivative of x^a which is ax^(a-1). But those aren't the same thing.

    The derivatve of e^x is e^x. Ring a bell?

    Good luck on that exam!
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