教材中有这样一道经典例(习)题:已知平面内的动点P与两定点A、B连线的斜率之积为定值,即kPA·kPB=非零常数m,求动点P的轨迹.若设两定点为A(-a,0)、B(a,0),则易知动点P的轨迹方程为mx2-y2=ma2(点A1、A2的坐标也满足).命题1当m<-1时,方程为x2a2+y2-ma2=1,轨迹是焦点在y轴上的椭圆; The textbook has such a classic example (Xi) problem: the known plane in the moving point P and the two fixed point A, B slope of the product of a fixed value, that kPA · kPB = non-zero constant m, the action point P If the two fixed points are set as A (-a, 0), B (a, 0), then the trajectory equation of the moving point P is mx2-y2 = ma2 (the coordinates of points A1 and A2 are also satisfied.) Proposition 1 When m <-1, the equation is x2a2 + y2-ma2 = 1, the trajectory is the oval with the focus on the y axis;