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Homework Help: Evalutating integerals

  1. Jan 31, 2009 #1
    1. The problem statement, all variables and given/known data
    I have to evaluate the integral of (x-9)4^xdx


    2. Relevant equations
    Integration by parts



    3. The attempt at a solution
    I setted the (x-9) as D and the 4^x as I. The problem is that im not sure what the antiderivative of 4^x would be. Im guessing its mostly like 4^x+1 all over x+1. If this is true, then there is another problem. Im not sure of how i could integrate 4^x+1(x+1)^-1. Help is desperate at this moment, since i only have 6 hours to submit my homework. Please give me support. Thanks.
     
  2. jcsd
  3. Jan 31, 2009 #2

    Dick

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    Science Advisor
    Homework Helper

    4^x is a lot like e^x. In fact, it is e^(ln(4)*x). That's easy to integrate.
     
  4. Jan 31, 2009 #3
    thank you very much for the assistance.
     
  5. Jan 31, 2009 #4
    Keep only one thread for one problem.

    What's the anti-derivative of e^(x)?
    What's the anti-derivative of e^(a.x)?
    So, a = ln(4)
     
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