依题得：（x-2m-1)^2+(y-m)^2+4m^2+5m+2-（2m+1)^2-m^2=0
(x-2m-1)^2+(y-M)^2+4m^2+5m+2-4m^2-4m-1-m^2=0
(x-2m-1)^2-(y-m)^2=m^2-m-1
要使方程为圆,即m^2-m-1>0
(m-1/2)^2>3/4
m>(3^0.5+1)/2或m