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Math Help - WHat is the integral of this function?

  1. #1
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    WHat is the integral of this function?

    \int x^{-3} e^{-2 \over x} dx

    Couldn't figure out what substitution to use for this one.
    Thanks.
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  2. #2
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    Ok!
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  3. #3
    Moo
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    Hello !

    Quote Originally Posted by chopet View Post
    \int x^{-3} e^{-2 \over x} dx

    Couldn't figure out what substitution to use for this one.
    Thanks.
    Use the substitution t=-\frac 2x

    \dots \implies dx=\frac 12 \cdot x^2 \ dt


    And you will see that the integral is -\frac 14 \ \int t e^t \ dt

    And here, use integration by parts
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  4. #4
    Senior Member nikhil's Avatar
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    use ILATE method that will give solution very easily
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  5. #5
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    Thanks guys. Sometimes when we subst, we get the whole exp term, seomtimes just the power. Substitution is really an art.
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