线与圆的位置关系常常涉及定点、定直线、定圆等“定”的问题,其本质就是曲线系,蕴含着数形结合思想、函数与方程思想等.下面举例说明.1.定点问题如y=kx是过定点O(0,0)的直线系,y=kx+b(b是常数)是过定点(0,b)的直线系,y=k(x-a)+b(a,b是常数)是过定点(a,b)的直线系,等等,那么,如何迅捷地找到直线所过的定点呢? The relationship between line and circle often involves the problem of fixed point, fixed line, fixed circle, etc. The essence of this is the curved line, which contains the idea of ​​combining numbers and shapes, the functions and equations, etc. The following examples illustrate: The problem is that if y = kx is a straight line with a fixed point O (0,0) and y = kx + b (b is a constant) is a straight line passing a fixed point (0, b) , b is a constant) is a fixed point (a, b) of the line, and so on, then how to quickly find the line over the fixed point?