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Homework Help: Substitution Rule for Indefinite Integrals

  1. May 27, 2008 #1
    1. The problem statement, all variables and given/known data
    [tex]\int2e^-^7^xdx[/tex]


    2. Relevant equations
    None


    3. The attempt at a solution

    [tex](\frac{-2}{7})(\frac{e^-^7^x}{-7})+C[/tex]


    This is as far as I can go, but the answer is:

    [tex]\frac{-2e^-^7^x}{7}+C[/tex]
     
  2. jcsd
  3. May 27, 2008 #2
    How did you get two 1/7 terms?
     
  4. May 27, 2008 #3
    I took the antiderivative of [tex]e^-^7^x[/tex].
     
  5. May 27, 2008 #4
    So, why do you have 1/7 * 1/7? Just do it again from scratch and you'll probably see what you did wrong.
     
  6. May 27, 2008 #5
    [tex]2\int e^{-7x}dx[/tex]

    [tex]-\frac 2 7\int -7e^{-7x}dx[/tex]

    You don't need to divide by another -7. It's already in standard form!
     
  7. May 27, 2008 #6
    I've got it now, thanks.:smile:
     
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