O(2,1),r=4
(1)
mx+2y-4m+2=0
圆心O到直线的距离h=|2m+2-4m+2|/√(4+m^2)=|4-2m|/√4+m^2)
12*(m+2/3)^2+48-12*(10/9)>0
12m^2+16m+48>0
16-16m+4m^2
O(2,1),r=4
(1)
mx+2y-4m+2=0
圆心O到直线的距离h=|2m+2-4m+2|/√(4+m^2)=|4-2m|/√4+m^2)
12*(m+2/3)^2+48-12*(10/9)>0
12m^2+16m+48>0
16-16m+4m^2