(文)已知等比数列{xn}的公比是不为1的正数,数列{yn}满足yn•logxn

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问题:

(文)已知等比数列{xn}的公比是不为1的正数,数列{yn}满足yn•logxna=2(a>0,a≠1),当y4=15,y7=9时,数列{yn}的前k项和最大,则k的值为 (  )
A.9B.10C.11D.12
考点:等比数列的通项公式数列求和的其他方法(倒序相加,错位相减,裂项相加等)数列的概念及简单表示法
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阅读短文,根据短文内容,选择恰当的答案回答问题。

Dear Mummy,

      How are you? I am fine at school. Tomorrow is National Day. We don't have to go to school. I am going

to take a trip with my friends in the morning. I am going to Zhongshan Park. I am going there by bike. It's near

our school. In the afternoon, I am going to the bookstore and buy some new books. In the evening, I am going

to watch TV. What are you going to do tomorrow? Can you tell me?

                                        Your son,

                                         Tom

1. What's the date tomorrow?

A. Oct. 1st

B. Nov. 1st

2. Where is Tom going on National Day morning?

A. The bookstore.

B. Zhongshan Park

3. How is Tom going to the park?

A. Ride a bike.

B. On foot

4. Is the park far from Tom's school?

A. Yes, it is.

B. No, it isn't.

5. What is Tom going to do in the bookstore?

A. Buy some new books.

B. Take a trip.

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下列各组物质中,互称为同系物的是(  )

A.氧气和臭氧

B.乙酸和醋酸

C.正丁烷和异丁烷

D.甲烷和丙烷

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院前急救的任务有( )

A.日常院前急救

B.灾害事故的院前急救

C.大型集会活动的救护待命

D.通讯网络中的枢纽任务

E.救护知识的普及

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施工、设计、监理和建设单位各方分别签字的质量验收证明,应由( )在工程竣工验收后3d内报送工程质量监督机构备案。

A.施工单位
B.建设单位
C.设计单位
D.监理单位

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在接触网没有停电接地的情况下,任何从业人员严禁登上各种机车()进行任何作业。

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