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Substitution in integral

  1. Aug 30, 2014 #1
    Hi members,

    see attached Pdf file.
    For a<0,write b=-a and let x=bt.Then

    My question:

    how becomes the denominator x+a to 1-t??? I don't see it

    Thank you
     

    Attached Files:

  2. jcsd
  3. Aug 30, 2014 #2

    HallsofIvy

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    The integral is
    [tex]\int_0^\infty \frac{x^{\mu-1}dx}{x+ a}[/tex]

    You attachment says "if a< 0 let b= -a" so becomes
    [tex]\int_0^\infty \frac{x^{\mu-1}dx}{x- b}[/tex]

    and "let x= bt". The denominator is x- b= bt- b= b(t- 1)

    Factor out "-b" leave 1- t in the denominator,
     
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