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Math Help - help for solving integral int_0^{infinity} exp(-x) / ((x+a)(x+b)) dx

  1. #1
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    help for solving integral int_0^{infinity} exp(-x) / ((x+a)(x+b)) dx

    Dear All,
    How to solve the following integral (see attachment)?
    a,b, are real scalars.
    Any help would be much welcome
    Thanks
    Attached Files Attached Files
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  2. #2
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    Re: help for solving integral int_0^{infinity} exp(-x) / ((x+a)(x+b)) dx

    You wrote it in LaTeX code in the title, why the PDF?

    What have you been able to do with this?

    -Dan
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    Re: help for solving integral int_0^{infinity} exp(-x) / ((x+a)(x+b)) dx

    PDF because it is easier to read.
    I could not find any similar integral in Gradshteyn and Ryzhik's Table of Integrals.
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    Forum Admin topsquark's Avatar
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    Re: help for solving integral int_0^{infinity} exp(-x) / ((x+a)(x+b)) dx

    With a few quick changes and the addition of [tex] tags we get:
    \int_0^{\infty} \frac{e^{-x}}{(x+a)(x+b)} dx

    Have you ever heard of the Laplace transform?

    -Dan
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  5. #5
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    Re: help for solving integral int_0^{infinity} exp(-x) / ((x+a)(x+b)) dx

    ok, I got it.
    There is no need for Laplace. Simply use partial fraction expansion and expand the integral into a sum of two integral. Each of them can be solved using the exponential integral function Ei.
    Thanks
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