C1
(x-2)²+(y-1)²=10
圆心(2,1),r1=√10
C2
(x-3)²+(y-1/2)²=37/4
圆心(3,1/2),r2=√37/2
圆心距d=√(1+1/4)=√5/5
r1+r2=√10+√37/2
r1-r2=√10-√37/2
则r1-r2