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Derivative of Exponential and Logarithmic Function Concept Question

  1. Nov 5, 2009 #1

    jacksonpeeble

    User Avatar
    Gold Member

    1. The problem statement, all variables and given/known data
    y=9-x


    2. Relevant equations



    3. The attempt at a solution
    dy/dx=-9-xln9

    We are provided with the answers. I do not understand the concept behind how to get from the question to the solution. What rule(s) are applied? If somebody could solve this single question, or a similar one, in a step-by-step method, I would greatly appreciate it.
     
  2. jcsd
  3. Nov 5, 2009 #2

    Mark44

    Staff: Mentor

    Do you know how to find d/dx(eu)? If so, you can rewrite 9-x as (eln 9)-x and use that derivative formula on it. You'll also want to use the fact that (ar)s = ars.

    Welcome back! Haven't heard from you for a while.
     
  4. Nov 5, 2009 #3

    jacksonpeeble

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    Gold Member

    Thank you, that is very helpful. It makes sense, but it really seems kind of roundabout... ah, well. Calculus...

    Thank you! Lately I've either been able to do my homework (or at least I've suffered in silence), although I'm taking AP Physics this year and I've posted some on that forum, and I occasionally try to contribute on the Pre-Calc boards when possible.
     
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