问题
选择题
设函数f1(x)=log4x-(
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答案
∵函数f1(x)=log4x-(
)x、f2(x)=log1 4
x-(1 4
)x的零点分别为x1、x2,1 4
∴0<x2<1<x1,
∴f1(x1)=log4x1-(
)x1=0,f2(x2)=log1 4
x2-(1 4
)x2=-log4x2-(1 4
)x2=log41 4
-(1 x2
)x2=0,1 4
而(
)x2 >(1 4
)x1,∴log4x1 <log41 4
,即x1<1 x2
,1 x2
∴0<x1x2<1,
故选A.