I can't understand the sum notation shown in Wikipedia or in this article:(adsbygoogle = window.adsbygoogle || []).push({});

http://mathforum.org/library/drmath/view/53159.html

I want to find the sum notation for (a+b+c)^n

however I can't understand the sum notation:

I don't understand the use of brackets or what they mean here and in the binomial theorem.

I think they are what Wikipedia calls the binomial coefficient:

http://en.wikipedia.org/wiki/Binomial_theorem

I also don't understand, is that they are taking the some from i,k,j to what? Shouldn't their be a number on top of the sigma?

I would appreciate the help!

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# Trinomial and Multinomial theorem

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