A.A B.B C.C D.D
A.a2-2a-2b-3=02 B.a2+2a+2b+5=0 C.a2+2b2+2a+2b+1=0 D.3a2+2b2+2a+2b+1=02
A.x2+y2-10x+9=0 B.x2+y2-10x+16=0 C.x2+y2+10x+16=0 D.x2+y2+10x+9=0
A.x+y+1=0 B.x-y-1=0 C.x+y-1=0 D.x-y+1=0
A.4 B.3 C.4 D.8