Question

到两定点A(-2,0),B(1,0)的距离之比等于2的点的轨迹方程为?

Answer 1

设动点为P(x,y)

则|PA|=2|PB|

|PA|^2=4|PB|^2

(x+2)^2+y^2=4[(x-1)^2+y^2]

x^2-4x+y^2=0

(x-2)^2+y^2=4