问题 填空题

若x02+y02+Dx0+Ey0+F>0,则点P(x0,y0)在圆x2+y2+Dx+Ey+F=0的______.

答案

∵x2+y2+Dx0+Ey0+F>0,

x02+y02+Dx0+Ey0+F

=(x0+

D
2
)2+(y0+
E
2
)
2
-
D2+E2-4F
4
>0,

(x0+

D
2
)2+(y0+
E
2
)
2
D2+E2-4F
4

∴点P(x0,y0)在圆x2+y2+Dx+Ey+F=0的外部.

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