圆C:x^2+y^2-6x+5=0
C(3,0),r=2
M(x,y)
k(AB)=y/x,k(CM)=y/(x-3)
k(AB)*k(CM)=-1
[y/(x-3)]*(y/x)=-1
(x-1.5)^2+y^2=2.25