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1\(5.6)+1\(5.6.7) + 1\(5.6.7.8)+ .

  1. Sep 17, 2006 #1
    1\(5.6)+1\(5.6.7) + 1\(5.6.7.8)+..............

    1\(5.6)+1\(5.6.7)+1\(5.6.7.8)+..............
     
  2. jcsd
  3. Sep 17, 2006 #2

    arildno

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    Well, rewrite this as:
    [tex]\frac{1}{5*6}+\frac{1}{5*6*7}+\frac{1}{5*6*7*8}++++=\frac{4!}{6!}+\frac{4!}{7!}+\frac{4!}{8!}+++=4!*(\sum_{n=0}^{\infty}\frac{1}{n!})-4!*(\sum_{n=0}^{5}\frac{1}{n!})[/tex]
    see if you can get somthing out of this.
     
  4. Sep 17, 2006 #3

    AKG

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    Hint:

    [tex]e^x = \sum _{n=0} ^{\infty} \frac{x^n}{n!}[/tex]
     
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