The middle term in a binomial expansion depends on whether the exponent 'n' is even or odd: if 'n' is even, there's one middle term, the $(\frac{n}{2} + 1)$ th term; if 'n' is odd, there are two middle terms, the $\frac{n+1}{2}$ and $\frac{n+3}{2}$ th terms.
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