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如图,D,E,F分别是△ABC的边AB,BC,CA的中点,则( ) A.++= ...
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如图,D,E,F分别是△ABC的边AB,BC,CA的中点,则( )
A.
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+
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+
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=
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B.
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+
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=
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C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101230927970823386/SYS201311012309279708233002_ST/8.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101230927970823386/SYS201311012309279708233002_ST/9.png)
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=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101230927970823386/SYS201311012309279708233002_ST/11.png)
D.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101230927970823386/SYS201311012309279708233002_ST/12.png)
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=
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A.
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函数f(x)对一切实数x,y均有f(x+y)-f(y)=(x+2y+1)x成立,且f(1)=0,
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