若三个球的表面积之比是1:4:9,则它们的体积之比是 .
考点分析:
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圆心为
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225226417449703/SYS201311012252264174497007_ST/0.png)
的圆与直线l:x+2y-3=0交于P、Q两点,O为坐标原点,且满足
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,则圆C的方程为( )
A.
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B.
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C.
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D.
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在下列关于直线l、m与平面α、β的命题中,真命题是( )
A.若l⊂β,且α⊥β,则l⊥α
B.若l⊥β,且α∥β,则l⊥α
C.若α∩β=m,且l⊥m,则l∥α
D.若l⊥β,且α⊥β,则l∥α
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直线x-2y-3=0与圆(x-2)
2+(y+3)
2=9交于E,F两点,则△EOF(O是原点)的面积为( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225226417449703/SYS201311012252264174497005_ST/0.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225226417449703/SYS201311012252264174497005_ST/1.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225226417449703/SYS201311012252264174497005_ST/2.png)
D.
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如果实数x、y满足条件
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225226417449703/SYS201311012252264174497004_ST/0.png)
,那么2x-y的最大值为( )
A.2
B.1
C.-2
D.-3
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若a,b是异面直线,直线c∥a,则c与b的位置关系是( )
A.相交
B.异面
C.平行
D.异面或相交
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