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已知函数f (x)=-x2-x4-x6,x1,x2,x3∈R且x1+x2<0,x...
已知函数f (x)=-x2-x4-x6,x1,x2,x3∈R且x1+x2<0,x2+x3<0,x3+x1<0,则f′(x1)+f′(x2)+f′(x3)的值是(f′(x)是f (x)的导数)( )
A.一定小于零
B.等于零
C.一定大于零
D.正负均有可能
考点分析:
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