(2007?咸安區(qū)模擬)已知點(diǎn)P(2,1)在圓C:x2+y2+ax-2y+b=0上,點(diǎn)P關(guān)于直線x+y-1=0的對(duì)稱(chēng)點(diǎn)也在圓C上,則實(shí)數(shù)a,b的值為( ?。?A.a=-3,b=3 B.a=0,b=-3 C.a=-1,b=-1 D.a=-2,
(2007?咸安區(qū)模擬)已知點(diǎn)P(2,1)在圓C:x2+y2+ax-2y+b=0上,點(diǎn)P關(guān)于直線x+y-1=0的對(duì)稱(chēng)點(diǎn)也在圓C上,則實(shí)數(shù)a,b的值為( )
A. a=-3,b=3
B. a=0,b=-3
C. a=-1,b=-1
D. a=-2,b=1
優(yōu)質(zhì)解答
由題意圓心C(
?,1)在直線x+y-1=0上,從而有-a
2+1-1=0,∴a=0,
∵點(diǎn)P(2,1)在圓C:x
2+y
2+ax-2y+b=0上,∴b=-3.
故選B.
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