(1)灵活应用“五”种重要的数学思想求数列问题:函数思想→数列是特殊的函数,其定义域是正整数集N*(或它的有限子集),值域是当自变量顺次从小到大取值时的对应的一系列函数值.其图象是一个个孤立的点.方程思想→在求解等差(比)数列中的基本量如a1,an,Sn,n,d(q)时,通常利用列方程组来解决.分类讨论思想→已知数列{an}的前n项和Sn,求an,要分n=1,n≥2进行讨论.若等比数列{an}的公比为字母q,则在求Sn时,要对q是否为1进行分 (1) flexible application of “five ” kinds of important mathematical ideas to solve the problem of columns: the function of thought → series is a special function, its domain is the set of positive integers N * (or its finite subset), the range is A series of function values ​​corresponding to variables in ascending order of magnitude. The image is an isolated point. Equation Idea → The basic quantity in solving an arithmetic sequence such as a1, an, Sn, n , d (q), it is usually solved by using the column equations. For the discussion of the first n terms and Sn of the known sequence {an}, we discuss an, n = 1, n≥2. Series {an} public as the letter q, then seeking Sn, q is a 1 to be divided