解二项式问题,首先要熟悉二项展开式的通项公式,其次还要掌握以下三个方面:(1)(a+b)~n的展开式的二项式系数之和为2~n.(2)对于(a+b)~n而言,当n为偶数时,其展开式中只有中间一项,即第(n/2+1)项的二项式系数最大;当n为奇数时,其展开式中中间两项,即第(n+1)/2和(n+3)/2项的二项式系数最大. To solve the binomial problem, first of all, we must be familiar with the general formula of the bi-exponential formula. Second, we must grasp the following three aspects: (1) The sum of the binomial coefficients of the expansion of (a+b)~n is 2~ n. (2) For (a+b)~n, when n is an even number, there is only a middle term in its expansion, ie, the binomial coefficient of the (n/2+1) term is the largest; when n In the case of an odd number, the middle two terms in the expansion formula, ie, the binomial coefficients of the (n+1)/2 and (n+3)/2 terms are the largest.