数列中有一类问题,递推公式或通项中含(-1)~n,需要分奇偶来讨论来解决问题。下面简单介绍一下这类题型的解答策略。一、整体操作所谓整体操作就是把(-1)~n看作整体进行运算或代换,这样做可以避免冗长复杂的分类讨论,只需将问题转化为特殊数列问题或求和问题,用适当的方法就能解决。这种做法的缺点是(-1)~n随n的变化而变化,在递推时不是一个常数,需要谨防符号的变化,很容易 There is a class of problems, recursion formula or general items containing (-1) ~ n, need to divide into odd and even to discuss to solve the problem. Here’s a brief introduction of such questions type strategy. First, the overall operation The so-called overall operation is to (-1) ~ n as a whole operation or substitution, so you can avoid the lengthy and complicated classification discussion, simply the problem into a special series of questions or summation problems, with appropriate The method can be solved. The disadvantage of this approach is that (-1) ~ n varies with n and is not a constant at recursion. It is easy to guard against symbol changes