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$\begingroup$

I know that

$(a+b)^2=a^2+b^2+2ab$ and $(a+b)^3=a^3+b^3+3ab(a+b)$

So i think it must be a formula that describes $(a+b)^n$, but I don't know what.

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    $(a+b)^n = \sum_{i=0}^n \binom{n}{i} a^i b^{n-i}$2012-03-17

1 Answers 1

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Use the Binomial Theorem:

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