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已知数列的前n项和(n为正整数)。
(1)令,求证数列是等差数列,
(2)求数列的通项公式;
(3)令。是否存在最小的正整数,使得对于都有恒成立,若存在,求出的值。不存在,请说明理由。

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已知等比数列的各项均为正数,且
(I)求数列的通项公式.
(II)设,求数列的前n项和.

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已知,数列是首项为a,公比也为a的等比数列,令,求数列的前项和

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(本题14分)已知等差数列满足的前n项和为,求的通项公式及;(2)若,求数列的前n项和.

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甲、乙两物体做匀速直线运动,它们的速度之比为3∶1,通过的路程之比为2∶3,那么甲、乙两物体运动的时间之比是
A.2∶9B.2∶1
C.9∶2D.1∶2

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一短跑运动员沿直线跑了10s,前4s内通过32m的路程,后6s通过60m的路程,这个运动员在10S内的平均速度是(   )
A.10m/sB.8m/sC.9.2m/sD.9m/s

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科目: 来源: 题型:阅读理解

When other nine-year-old kids were playing games, she was working at a petrol station. When other teens were studying or going out, she struggled to find a place to sleep on the street. But she overcame these terrible setbacks to win a highly competitive scholarship(奖学金)and gain entry to Harvard University. And her amazing story has inspired a movie, “Homeless to Harvard: The Liz Murray Story”, shown in late April.
 Liz Murray, a 22-year-old American girl, has been writing a real-life story of willpower and determination. Liz grew up in the shadow of two drug-addicted(吸毒)parents. There was never enough food or warm clothes in the house. Liz was the only member of the family who had a job. Her mother had AIDS and died when Liz was just 15 years old. The effect of that loss became a turning point in her life. Connecting the environment in which she had grown up with how her mother had died, she decided to do something about it.
 Liz went back to school. She threw herself into her studies, never telling her teachers that she was homeless. At night, she lived on the streets.“What drove me to live on had something to do with understanding, by understanding that there was a whole other way of being. I had only experienced a small part of the society,”she wrote in her book Breaking Night.
 She admitted that she used envy to drive herself on. She used the benefits that come easily to others, such as a safe living environment, to encourage herself that “next to nothing could hold me down”. She finished high school in just two years and won a full scholarship to study at Harvard University. But Liz decided to leave her top university a couple of months earlier this year in order to take care of her father, who has also developed AIDS. “I love my parents so much. They are drug addicts. But I never forget that they love me all the time.”
  Liz wants moviegoers to come away with the idea that changing your life is “as simple as making a decision”.
【小题1】In which order did the following things happen to Liz?
  a. Her mother died of AIDS.    b. She worked at a petrol station.
  c. She got admitted into Harvard. d. The movie about her life was put on.
  e. She had trouble finding a place to sleep.
A.b, a, e, c, d  B.a, b, c, e, dC.e, d, b, a, cD.b, e, a, d, c
【小题2】The main idea of the passage is ________.
A.how Liz managed to enter Harvard UniversityB.what a hard time Liz had in her childhood
C.why Liz loved her parents so muchD.how Liz struggled to change her life
【小题3】What actually made her go towards her goal?
A.Envy and encouragement.B.Willpower and determination.
C.Decisions and understanding.D.Love and respect for her parents.
【小题4】When she wrote “What drove me to live on...I had only experienced a small part of the society”, she meant that ________.
A.she had little experience of social lifeB.she could hardly understand the society
C.she would do something for her own lifeD.she needed to travel more around the world

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完成下列的单位换算
(1)一张纸的厚度为84µm="________m   "         (2)一节课45min="______h   "
(3)小汽车行驶的速度为72km/h=_______m/s

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填写合适的单位:
(1)课桌的高度是0.75______       (2)小明的100米的成绩为14.7______      
(3) 一个成年人正常步行的速度大约4.5_______

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如图所示的是摩托车引擎后安装的消声器的结构图.摩托车安装消声器是采用的是     处来减弱噪声的。

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