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数列在中学数学阶段占据不小的分值,它与其他章节有着一定的联系。不论形式怎么变化,解决数列问题就必须确定他的通项公式。下面介绍三种常用的方法。一、归纳猜想法归纳猜想法是通过观察告诉的前几项,找出他们的特点,总结出通项表达式,最后去证明猜想的正确性。例:设数列??na的前n项和为Sn,且方程x2—anx—an=0有一个根为Sn—1,n∈N*,(1)求a1,a2;(2)求??na的通项公式。解析:本题条件中有关于Sn—1的方程,通过S1、S2求
The number of maths in secondary school occupy a small score, it has some links with other chapters. No matter how the form changes, to solve the sequence of questions, we must determine his general formula. Here are three commonly used methods. First, to conclude that the conjecture method of conjecture is by observing the first few tell, find out their characteristics, summed up the general expression, and finally to prove the correctness of conjecture. Example: Suppose the first n terms of Sn and the array n is Sn, and the equation x2-anx-an = 0 has a root Sn-1, n∈N *, (1) Find a1, a2; (2) na’s general formula. Analysis: The conditions of this article on the Sn-1 equation, through S1, S2 seeking