答：
A(3,3),B(6,1),设P在y轴上,且AP=BP
设点P为（0,p）
AP^2=BP^2：
(3-0)^2+(3-p)^2=(6-0)^2+(1-p)^2
9+9-6p+p^2=36+1-2p+p^2
18-6p=37-2p
6p-2p=18-37
4p=-19
p=-19/4