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Re: Summations



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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