- #1

geor

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**[SOLVED] Changing order of a double sum**

Hello everybody,

I am a bit confused here, any help would be greatly appreciated..

I have this double sum:

[tex]\sum_{i=0}^{n-1}a_i \sum_{j=0}^{i} {i \choose j} b^{i-j}x^j[/tex]

How can I take x out of the inner sum?

Thank you very much in advance...

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