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设x>y>0>z,空间向量=(x,,3z),=(x,+,3z),且x2+9z2=...
设x>y>0>z,空间向量
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645011_ST/0.png)
=(x,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645011_ST/1.png)
,3z),
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645011_ST/2.png)
=(x,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645011_ST/3.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645011_ST/4.png)
,3z),且x
2+9z
2=4y(x-y),则
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645011_ST/5.png)
•
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645011_ST/6.png)
的最小值是( )
A.2
B.4
C.2
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645011_ST/7.png)
D.5
考点分析:
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645007_ST/2.png)
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645006_ST/0.png)
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183821039664566/SYS201310241838210396645006_ST/1.png)
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