A=(0,b)

AP=(4/3,2b/3)
圆心为O
AO=(2/3,b/3)
圆方程为
(x-2/3)^2+(y-b/3)^2=(4+b^2)/9

代入y=0

(x-2/3)^2=(b^2+4-b^2)/9

(x-2/3)^2=4/9
x=4/3或0
焦点不可能在原点,右焦点为 (4/3,0)


a^2-b^2=16/9

16/9a^2+1/9=1
a^2=2
b^2=2/9

x^2/2+9y^2/2=1