1、x^2+y^2-2x-4y+m＝0(x-1)^2+(y-2)^2=5-m5-m>0m<52、ImnI＝2根号5/5r=根号(5-m) d=I1+4-4I/根号5=根号5/5r^2=d^2+ImnI^2/45-m=1/5+1/5m=23/5
