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I have the following sum

[tex]\sum n - n_1 + 1 [/tex]

which I split up in two independent sums

[tex]\sum_{n_1=0}^N n + 1 - \sum_{n_1=0}^N n_1[/tex]

the last sum can be written as

[tex]0.5*n(n+1) [/tex]

but how to rewrite the first sum any hints appreciated. The final answer is

0.5(n+1)(n+2)

but as stated above I have some problems getting there.

Any help or advice appreciated thanks in advance

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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# Homework Help: Rewriting a sum

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