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MathGroup Archive 2007

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Re: Summations

  • To: mathgroup at
  • Subject: [mg78248] Re: Summations
  • From: dh <dh at>
  • Date: Wed, 27 Jun 2007 05:17:56 -0400 (EDT)
  • References: <f5qme1$46g$>

Hi Sima,

what problem do you have that you can  not do it yourself?

Sum[i a^i,{i,1,n}] gives (a (1-a^n-a^n n+a^(1+n) n))/(-1+a)^2

Sum[i n^i+n^3,{i,1,m}] gives m n^3+(n (1-n^m-m n^m+m n^(1+m)))/(-1+n)^2

hope this helps, Daniel

Sima wrote:

> Can someone please solve this summations:


> Summation(from i=1 to n) (i * a ^ i)


> Summation(from i=1 to m) (i * n ^ i + n ^ 3)


> you can mail me sollutions. Thanks



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