由等差数列{an}的通项公式an=a1+(n-1)d可得an=nd+(a1-d)(n∈N),显然,当d≠0时,an是关于自然数n的一次函数.它的几何意义是以d为斜率,在y轴上的截距为a1-d的一条直线上的点集.点的坐标为(n,an),其中n∈N. From the general term an=a1+(n-1)d of the arithmetic series {an}, an=nd+(a1-d)(n∈N) is obtained. Obviously, when d≠0, an is about the natural number n. A first-order function. Its geometric meaning is a set of points on a straight line with d as the slope and the intercept on the y-axis is a1-d. The coordinates of the point are (n, an), where n∈N.