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A x=0与x=1都是f(x)的第一类间断点． B x=0与x=1都是f(x)的第二类间断点． C x=0是f(x)的第一类间断点，x=1是f(x)的第二类间断点． D x=0是f(x)的第二类间断点，x=1是f(x)的第一类间断点．

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A 高阶无穷小 B 低阶无穷小 C 同阶但非等价的无穷小 D 等价无穷小

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下列函数中，在x=0处不可导的是( ).

A f(x)=|x|sin|x| B <img width="218" height="22" src="https://www.beizhujiaoyu.com/uploads/202208/20210917234739_1638.jpg" /> C f(x)=|x|cos|x| D <img width="176" height="22" src="https://www.beizhujiaoyu.com/uploads/202208/20210917234739_5711.jpg" />

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设k>0，则函数f(x)=lnx-+k的零点个数为( )．

A 0个 B 1个 C 2个 D 3个

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A -2 B -1 C 1 D 2

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A 1 B <img width="19" height="40" src="https://www.beizhujiaoyu.com/uploads/202208/20211031002155_8835.jpg" /> C <img width="24" height="20" src="https://www.beizhujiaoyu.com/uploads/202208/20211031002157_7596.jpg" /> D <img width="25" height="48" src="https://www.beizhujiaoyu.com/uploads/202208/20211031002158_1035.jpg" />

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的取值

A (-2，2) B 2 C (2，+∞) D (-∞，-2)

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设(X，Y)服从二维正态分布，其边缘分布为X～N(1，1)，Y～N(2，4)，X，Y的相关系数为pxy=-0.5，且P(aX+bY≤1)=0.5，则( )．

A a=<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20211030231235_6636.gif" />,b=-<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20211030231230_6480.gif" /> B a=<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20211030231230_6480.gif" />,b=-<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20211030231235_6636.gif" /> C a=-<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20211030231230_6480.gif" />,b=<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20211030231235_6636.gif" /> D a=<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20211030231235_6636.gif" />,b=<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20211030231230_6480.gif" />

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已知总体X的期望E(X)=0，方差D(X)=σ2．X1，…，Xn是来自总体X的简单随机样本，其均值为，则可以作出数学期望等于σ2的统计量是

A <img width="151" height="46" src="https://www.beizhujiaoyu.com/uploads/202208/20210917223625_6058.jpg" /> B <img width="179" height="46" src="https://www.beizhujiaoyu.com/uploads/202208/20210917223626_0893.jpg" /> C <img width="80" height="46" src="https://www.beizhujiaoyu.com/uploads/202208/20210917223627_7133.jpg" /> D <img width="108" height="46" src="https://www.beizhujiaoyu.com/uploads/202208/20210917223628_2612.jpg" />

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A <img width="74" height="21" src="https://www.beizhujiaoyu.com/uploads/202208/20211118123937_0709.jpg" /> B <img width="115" height="37" src="https://www.beizhujiaoyu.com/uploads/202208/20211118123938_6334.jpg" /> C <img width="115" height="37" src="https://www.beizhujiaoyu.com/uploads/202208/20211118123939_2584.jpg" /> D <img width="115" height="37" src="https://www.beizhujiaoyu.com/uploads/202208/20211118123940_8990.jpg" />

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