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函数f(x)的定义域为D,若存在闭区间[a,b]⊆D,使得函数f(x)满足:①f...
函数f(x)的定义域为D,若存在闭区间[a,b]⊆D,使得函数f(x)满足:①f(x)在[a,b]内是单调函数;②f(x)在[a,b]上的值域为[2a,2b],则称区间[a,b]为y=f(x)的“倍值区间”.下列函数中存在“倍值区间”的有( )
①f(x)=x
2(x≥0);
②f(x)=e
x(x∈R);
③f(x)=
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(x≥0);
④f(x)=
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.
A.①②③④
B.①②④
C.①③④
D.①③
考点分析:
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