在解等差、等比数列题时 ,会碰到一些根据已知条件 ,基本量 (首项ａ1、公差ｄ或公比ｑ、项数ｎ)无法确定 ,或从局部考虑不好下手或运算量较大的题 .这些题从整体的角度来考虑 ,往往可寻得简捷的解题途径 .下面具体介绍这种思想方法 .1　运用等差、等比数列的通项公式或求和公式 When solving equations of equal or odd number, you will encounter some basic conditions (first item a1, tolerance d or common ratio q, number of items n) that cannot be determined based on known conditions. Large-scale questions. These questions are considered from an overall perspective, and you can often find a simple solution to the problem. The following specific introduction to this method of thinking.1 Use the arithmetic of the difference equation or the sum formula