圆C:x2+y2+Dx-6y+1=0,圆心为(-D/2,3).
∵点P、Q在圆上且关于直线x-y+4=0对称,
∴圆心(-D/2,3)在直线上x-y+4=0.代入得D=2.
圆C:x2+y2+2x-6y+1=0,即圆C:(x+1)2+(y-3)2=9,
圆C:x2+y2+Dx-6y+1=0,圆心为(-D/2,3).
∵点P、Q在圆上且关于直线x-y+4=0对称,
∴圆心(-D/2,3)在直线上x-y+4=0.代入得D=2.
圆C:x2+y2+2x-6y+1=0,即圆C:(x+1)2+(y-3)2=9,