Field/Binomi/Explained/Fact/Proof/Exercise

Prove the general binomial formula, that is, the formula

$(a+b)^{n}=\sum _{k=0}^{n}{\binom {n}{k}}a^{k}b^{n-k}$

for ${}n\in \mathbb {N}$ and arbitrary elements ${}a,b\in K$ in a field ${}K$.

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