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当x→0时，x-tanx与xk是同阶无穷小，则k=( )．

A 1 B 2 C 3 D 4

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已知方程x5-5x+k=0有3个不同的实根，则k的取值范围是( )．

A (-∞，-4) B (4，+∞) C [-4，4] D (-4，4)

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已知微分方程y”+ay'+by=cex的通解为y=(C1+C2x)e-x+ex，则a，b，c依次为( )．

A 1，0，1 B 1，0，2 C 2，1，3 D 2，1，4

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A <img width="153" height="47" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182804_6168.jpg" /> B <img width="154" height="47" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182806_4449.jpg" /> C <img width="157" height="47" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182806_8837.jpg" /> D <img width="157" height="47" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182808_7106.jpg" />

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设A是四阶矩阵，A*是A的伴随矩阵，若线性方程Ax=0的基础解系中只有2个向量，则A*的秩是( )．

A 0 B 1 C 2 D 3

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设A是三阶实对称矩阵，E是三阶单位矩阵，若A2+A=2E，且|A|=4，则二次xTAx的规范形为( )．

A <img width="122" height="38" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182809_0826.gif" /> B <img width="116" height="38" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182810_9606.gif" /> C <img width="108" height="38" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182811_3199.gif" /> D <img width="120" height="38" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182813_1950.gif" />

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设A，B为随机事件，则P(A)=P(B)的充分必要条件是( )．

A P(A∪B)=P(A)+P(B) B P(AB)=P(A)P(B) C P(A<img width="20" height="35" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182813_8386.gif" title="" align="" alt="" />)=P(B<img width="20" height="35" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182815_4293.gif" title="" align="" alt="" />) D P(AB)=P(<img width="20" height="35" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182815_4293.gif" title="" align="" alt="" /><img width="20" height="35" src="https://www.beizhujiaoyu.com/uploads/202208/20210429182813_8386.gif" title="" align="" alt="" />)

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设随机变量X和Y相互独立，且都服从正态分布N(μ，σ2)，则P{|X-Y|

A 与μ无关，而与σ2有关 B 与μ有关，而与σ2无关 C 与μ，σ2都有关 D 与μ，σ2都无关

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