众所周知,理解数列的概念,了解数列通项公式的意义,了解递推数列的递推公式并能根据递推公式写出数列的前几项;理解等差数列的概念,掌握等差数列的通项公式与前n项和的公式,类比地理 As we all know, understand the concept of series, understand the meaning of series general formulas, understand the recursive formulas of recursive series, and write the first few items of the series according to the recursive formula; understand the concept of arithmetic sequences, and master the sequence of arithmetic sequences. Formula and formula of the first n terms, analogical geography