数列是中学数学的一个重要内容 ,在高考及会考中均占有一定比例 ,学生在解题过程中 ,一不小心往往会掉进“陷阱” .现举例说明这些常见错误 ,以便在教学中引起注意 .例 1　求和 :1+ 3+ 32 +… + 3ｎ.误解 :Ｓｎ=1·( 1- 3ｎ)1- 3=12 ( 3ｎ- 1) .剖析 :在数列试题中 ,项数也是考 The series is an important part of middle school mathematics. It occupies a certain percentage of college entrance examinations and college entrance examinations. Students often fall into the “trap” during the process of solving a problem. Now these common mistakes are illustrated to attract attention in teaching. Example 1 Summation: 1+ 3+ 32 +... + 3n. Misunderstanding: Sn = 1 (1 - 3n) 1 - 3 = 12 ( 3n - 1). Analysis: In the series of questions, the number of items is also