向量MP=向量ON
N(x1,y1)
P(x,y)
x+3=x1;y-4=y1则
(x+3)^2+(y-4)^2=4
当N在直线OM上时x+3=±6/5（舍去）,则x≠-9/5且x≠-21/5
综上,P的轨迹方程为
(x+3)^2+(y-4)^2=4,x≠-9/5且x≠-21/5