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Homework Help: Simple integration

  1. Mar 7, 2006 #1
    Could anyone explain to me very simply by means of a mechanical (formula) approach maybe why the integration of -x / (x^2 + 5) gives - 1/2 ln l x^2 + 5 l
     
  2. jcsd
  3. Mar 7, 2006 #2

    VietDao29

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    Homework Helper

    One big advice for you, Natasha1 is that, you should open your book, and re-read the chapter that teaches you the u-substitution. read and try to understand the concept, then move on to some examples, try to understand them. And finally, you should pratice solving some integrals that involve the u-substitution.
    For this problem, you should let u = x2 + 5 => du = 2xdx
    So the whole integral becomes:
    [tex]- \int \frac{xdx}{x ^ 2 + 5} = - \frac{1}{2} \int \frac{du}{u}[/tex].
    Can you go from here?
    ---------------
    But please, hear me, it won't do any harm to you if you try to re-read the textbook, and try to understand it...
     
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