截距定义,高中解析几何课本是在P19给出的。由于这个定义是放在圆括号内,以致未能引起学生应有的重视,因而望文生义,把截距曲解为距离,笔者有感于此,认为要正确理解截距的定义,只注意圆括号内“b是直线l在y轴上的截距”是不够的,必须和圆括号前“直线l与y轴交点(0,b)”相联系,这样就不难看出截距是用坐标来定义的。即直线l与y轴交点(0,b)的纵坐标b,是直线在y轴上的截距,依此类推,直线l与x轴交点(a,0)的横坐标a, Intercept definition, high school analytic geometry textbook is given in P19. Because this definition is placed in parentheses, it fails to attract students’ due attention. Therefore, the author interprets the intercept as a distance because of the meaning of the text. The author feels this and believes that the definition of the intercept must be correctly understood and only the parentheses should be considered. “b is the intercept of the line l on the y-axis” is not enough, must be associated with the “line 1 and y-axis intersection (0, b)” before the parentheses, so it is not difficult to see that the intercept is defined by coordinates of. That is, the ordinate b of the intersection point of the straight line l and the y axis (0, b) is the intercept of the straight line on the y axis, and so on, the abscissa a of the intersection of the line l and the x axis (a, 0),