设二维随机变量(U,V)的联合概率密度为 求证:(Ⅰ) X=U+V服从正态分布

题型:单项选择题

问题:

设二维随机变量(U,V)的联合概率密度为


求证:(Ⅰ) X=U+V服从正态分布; (Ⅱ) Y=U2+V2服从指数分布.

考点:普通考研考研数学(三)考研数学三
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病历摘要:患者男性,52岁,工人,因“呼吸急促,喉中哮鸣有声一周”来诊。患者哮喘病史已十一年,每因天冷或受寒易发,至夏季则缓解。一周前因受寒致哮喘再作,现症见:呼吸急促,喉中哮鸣有声,胸膈满闷如窒,咳不甚,痰少咯吐不爽,面色晦暗带青,口不渴,或渴喜热饮,形寒怕冷,舌苔白滑,脉弦紧或浮紧。

若以射干麻黄汤治疗该患者,该方剂组成有哪些药物?()

A.射干、细辛

B.干姜、紫菀

C.半夏、麻黄

D.桔梗、胆星

E.大枣

F.白果、杏仁

G.款冬花、五味子

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中共二大第一次明确提出彻底的民主革命纲领,这一纲领的主要内容包括

①实现 * * 主义             ②统一中国为真正的民主共和国 

③打倒军阀                 ④推翻国际帝国主义的压迫

A.①②③

B.①②④

C.②③④

D.①②③④

题型:单项选择题

Every year, British newspapers report on the stranger questions asked in Oxbridge (Oxford & Cambridge) interviews. Often, though, these questions are not as strange as they first seem. And they are all designed to give applicants (申请者) a chance to think.

Arriving for her first Oxford interview, my sister Jen saw that there was only one chair in the waiting room. On the chair was a large fork. Jen had heard about the strange things in Oxbridge interviews, and believed that this was a test. “What if they’re watching me?” she thought. “If I move the fork, it will show initiative (主动性); if I don’t move it, it will show that I can easily fit into new situations.” In the end, she sat uncomfortably on the edge of the chair!

Applicants must be prepared for the unexpected. Now it was Jen’s turn. She was handed a monkey skull (颅骨) and asked to talk about it. At first, this seemed unfair --- what could she say? But she soon calmed down, started thinking, and found that there was plenty to talk about.

Oxbridge interviews are designed to find out how you think, not just what you think. And there are no wrong answers. Jen learnt that, and she passed the interview. What advice does she give? “ Don’t be nervous, and be prepared for the unexpected!”

小题1:According to British newspapers, questions for Oxbridge applicants are very _____. 

A.unfair

B.normal

C.easy

D.strange小题2:On her first interview, Jen ____ after she entered the waiting room.

A.moved the fork

B.sat down on the fork

C.sat down on the chair

D.moved the chair小题3:Jen learned that it was very important to _____ in order to pass the Oxbridge interviews.

A.make up new situation

B.show how one thinks

C.describe what one hears

D.talk about various monkeys小题4:The writer uses a(n) ____ to introduce how Oxbridge applicants are interviewed.

A.example

B.guess

C.experiment

D.survey

题型:单项选择题

每一张凭证的入库,分发,收到,使用都可以通过()实现。

A.最小可用凭证查询

B.现金收付查询

C.尾箱操作记录查询

D.凭证状态查询

题型:单项选择题

目前螺杆泵采油按驱动方式分为()螺杆泵和封面驱动井下螺杆泵两种。

A、潜油

B、潜油电动

C、单

D、双

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