Can any one help me please (it's very urget)?

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- May 1st 2005, 09:40 PM #1

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## Sum problem!

Hi all

I have the following problem, i have attached the following equation into a file.

lets suppused i have the following vector :

A={10,20,50,60,70,49,21,23}

how i solve the equation (my main problem is how to threat the double sum function with diffrent indexies i.e. i,j) ?

Best Regreats

- May 4th 2005, 05:39 AM #2

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- May 4th 2005, 09:50 AM #3

- May 4th 2005, 09:45 PM #4

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- May 5th 2005, 09:26 AM #5Originally Posted by
**cobra**

Write sum'_j to indicate that the sum is over j, but skips the term j=i.

There are n+1 terms in sum_i and n terms in sum'_j.

Let A = sum_i Ai = sum_j Aj. Thus sum'_j Aj = A - Ai. Then

sum_i(sum'_j(Ai-Aj))

= sum_i(nAi - sum'_j Aj)

= sum_i(nAi - (A-Ai))

= sum_i((n+1)Ai - A)

= (n+1)sum_i (Ai) - (n+1)A

= 0.

- May 5th 2005, 09:48 PM #6

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