设B(x0,y0),P(x,y)
因为BP:PA=1:2=1/2,所以
x=[x0+(1/2)*3]/(1+1/2)=(2x0+3)/3,
y=[y0+(1/2)*1]/(1+1/2)=(2y0+1)/3.
--->x0=3(x-1)/2,y0=(3y-1)/2
因为得B在圆上,所以[3(x-1)/2]^2+[(3y-1)/2]^2=1
--->9(x-1)^2+(3y-1)^2=1.即为所求轨迹方程
--->(x-1)^2+(y-1/3)^2=1/9
设B(x0,y0),P(x,y)
因为BP:PA=1:2=1/2,所以
x=[x0+(1/2)*3]/(1+1/2)=(2x0+3)/3,
y=[y0+(1/2)*1]/(1+1/2)=(2y0+1)/3.
--->x0=3(x-1)/2,y0=(3y-1)/2
因为得B在圆上,所以[3(x-1)/2]^2+[(3y-1)/2]^2=1
--->9(x-1)^2+(3y-1)^2=1.即为所求轨迹方程
--->(x-1)^2+(y-1/3)^2=1/9