等差数列的通项a．和前n项和S．都可以看作为n的函数，下面就从函数的图象出发，谈一谈如何利用数形结合的思想来处理等差数列的有关问题．（1）等差数列的通项公式表明点（n，an）（n=1,2，…）共线于y=dx＋a1-d上．例1设2和3是某等差数列中的两项，试证明此数列中的任何一项? The general term of an arithmetic progression a. And the first n items and S. Can be seen as a function of n, the following starting from the function of the image, talk about how to use the idea of ​​combination of number and shape to deal with the problem of arithmetic series. (1) The general term formula for the arithmetic progression shows that the points (n, an) (n=1, 2, ...) are collinear to y=dx+a1-d. Example 1 Let 2 and 3 be two items in an arithmetic progression. Try to prove any one of the series.