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数列是高中数学的主干内容,是历年高考考查的重点与热点.对数列的学习,既要加强对概念的深刻理解,又要重视运算技能的训练,从而减少在解题中不该发生的错误.本文就数列问题中的几类容易失分、丢分点进行分类解析,旨在降低其居高不下的错误率.一、忽视n的取值变化很多数列问题的已知条件中有一些关于a_n及S_n的表达式,在递推时只顾递推,而未加注意n的取值变化,将导致错误的发生.例1已知正项数列{a_n}中,S_1=2,当n≥2时S_n=2a_n,
The number sequence is the main content of high school mathematics, which is the focus and hot spot of the college entrance examination in the past years.As for the study of the number sequence, it is necessary to strengthen the deep understanding of concepts and the training of computing skills so as to reduce the errors that should not occur in solving problems In this paper, we analyze the categorical analysis of several kinds of easy-to-lose points and dropping points in the sequence problem to reduce its high error rate.First, neglecting the change of the value of n Some of the known conditions of many sequence problems a_n and S_n, recursion only recursion, without noticing the value of n changes, will lead to errors.Example 1 Known positive sequence {a_n}, S_1 = 2, when n ≥ 2 When S_n = 2a_n,