第一篇:(新Ⅰ)2018年高考数学总复习专题06数列分项练习理
专题06 数列
一.基础题组
1.【2013课标全国Ⅰ,理7】设等差数列{an}的前n项和为Sn,若Sm-1=-2,Sm=0,Sm+1=3,则m=().
A.3 B.4 C.5 D.6 【答案】C 【解析】∵Sm-1=-2,Sm=0,Sm+1=3,∴am=Sm-Sm-1=0-(-2)=2,am+1=Sm+1-Sm=3-0=3.∴d=am+1-am=3-2=1.∵Sm=ma1+又∵am+1=a1+m×1=3,∴mm1m1×1=0,∴a1.22m1m3.∴m=5.故选C.22.【2012全国,理5】已知{an}为等比数列,a4+a7=2,a5a6=-8,则a1+a10=()A.7 B.5 C.-5 D.-7 【答案】D
3.【2008全国1,理5】已知等差数列an满足a2a44,a3a510,则它的前10项的和S10()A.138 B.135
C.95
D.23 【答案】C.【解析】由a2a44,a3a510a14,d3,S1010a145d95.4.【2013课标全国Ⅰ,理14】若数列{an}的前n项和Sn=__________.【答案】(-2)n-
121an,则{an}的通项公式是an33 【解析】∵Sn①-②,得an2121an,①∴当n≥2时,Sn1an1.② 333322aanan1,即n=-2.33an1∵a1=S1=21a1,∴a1=1.33n-1∴{an}是以1为首项,-2为公比的等比数列,an=(-2).5.【2009全国卷Ⅰ,理14】设等差数列{an}的前n项和为Sn.若S9=72,则a2+a4+a9=___________.【答案】24 【解析】∵S9729(a1a2),∴a1+a9=16.2∵a1+a9=2a5,∴a5=8.∴a2+a4+a9=a1+a5+a9=3a5=24.6.【2011全国新课标,理17】等比数列{an}的各项均为正数,且2a1+3a2=1,a329a2a3.(1)求数列{an}的通项公式;
(2)设bn=log3a1+log3a2+…+log3an,求数列{1}的前n项和. bn(2)bnlog3a1log3a2log3an(12n)n(n1)故212112(),bnn(n1)nn111b1b211112(1)()bn223112n().nn1n112n所以数列的前n项和为.bn1n7.【2010新课标,理17】(12分)设数列{an}满足a1=2,an+1-an=3·2(1)求数列{an}的通项公式;
(2)令bn=nan,求数列{bn}的前n项和Sn.【解析】(1)由已知,当n≥1时,an+1=(an+1-an)+(an-an-1)+…+(a2-a1)]+a1=3(2
2n-1
2n-1
.+
22n-
3+…+2)+2=2
2(n+1)-1
.而a1=2,所以数列{an}的通项公式为an=2(2)由bn=nan=n·232n-1
2n-1
.知
2n-1Sn=1·2+2·2+3·2+…+n·223
575
.①
2n+1从而2·Sn=1·2+2·2+3·2+…+n·2①-②,得
(1-2)Sn=2+2+2+…+2即Sn=235
2n-1
.②
-n·2
2n+1,12n+1(3n-1)2+2]. 98.【2005全国1,理19】设等比数列{an}的公比为q,前n项和Sn>0(n=1,2,…)(1)求q的取值范围;(2)设bnan23an1,记{bn}的前n项和为Tn,试比较Sn和Tn的大小.2
解①式得q>1;解②,由于n可为奇数、可为偶数,得-1 试题分析:(Ⅰ)先用数列第项与前项和的关系求出数列{an}的递推公式,可以判断数列{an}是等差数列,利用等差数列的通项公式即可写出数列{an}的通项公式;(Ⅱ)根据(Ⅰ)数列{bn}的通项公式,再用拆项消去法求其前项和.【考点定位】数列前n项和与第n项的关系;等差数列定义与通项公式;拆项消去法 10.【2016高考新课标理数3】已知等差数列{an}前9项的和为27,a10=8,则a100=(A)100(B)99(C)98(D)97 【答案】C 【解析】 试题分析:由已知,C.9a136d27,所以a11,d1,a100a199d19998,故选a19d8【考点】等差数列及其运算 【名师点睛】等差、等比数列各有五个基本量,两组基本公式,而这两组公式可看作多元方程,利用这些方程可将等差、等比数列中的运算问题转化为解关于基本量的方程(组),因此可以说数列中的绝大部分运算题可看作方程应用题,所以用方程思想解决数列问题是一种行之有效的方法.二.能力题组 1.【2011全国,理4】设Sn为等差数列{an}的前n项和,若a1=1,公差d=2,Sk+2-Sk=24,则k=()A.8 B.7 C.6 D.5 【答案】D 2.【2006全国,理10】设{an}是公差为正数的等差数列,若a1+a2+a3=15,a1a2a3=80则a11+a12+a13=() (A)120(B)105(C)90(D)75 【答案】B 【解析】 3.【2012全国,理16】数列{an}满足an+1+(-1)an=2n-1,则{an}的前60项和为__________. 【答案】1 830 【解析】:∵an+1+(-1)an=2n-1,nn∴a2=1+a1,a3=2-a1,a4=7-a1,a5=a1,a6=9+a1,a7=2-a1,a8=15-a1,a9=a1,a10=17+a1,a11=2-a1,a12=23-a1,…,a57=a1,a58=113+a1,a59=2-a1,a60=119-a1,∴a1+a2+…+a60=(a1+a2+a3+a4)+(a5+a6+a7+a8)+…+(a57+a58+a59+a60)=10+26+42+…+234= 15(10234)1830. 24.【2014课标Ⅰ,理17】 已知数列an的前项和为Sn,a11,an0,anan1Sn1,其中为常数,(I)证明:an2an; (II)是否存在,使得an为等差数列?并说明理由.【答案】(I)详见解析;(II)存在,4.5.【2009全国卷Ⅰ,理20】 在数列{an}中,a1=1,an+1=(11n1)an+n.n2(Ⅰ)设bnan,求数列{bn}的通项公式; n(Ⅱ)求数列{an}的前n项和Sn.【解析】(Ⅰ)由已知得b1=a1=1,且 an1an11n,即bn1bnn.n1n22从而b2b12n11111于是bnb12n12n1(n≥2).2222 bnbn111,b3b22,…… 221(n≥2).又b1=1.故所求的通项公式bn2(Ⅱ)由(Ⅰ)知ann(2令Tnn12n1.12n)2nn1n2n1.2k1nkk1,则2Tn2k1kk2.于是Tn=2Tn-Tn= 2k0n11k1n2n1=4n2.又n12(2k)n(n1),k1所以Snn(n1)n24.2n1?an的最大值6.【2016高考新课标理数1】设等比数列{an}满足a1+a3=10,a2+a4=5,则a1a2鬃为.【答案】64 【考点】等比数列及其应用 【名师点睛】高考中数列客观题大多具有小、巧、活的特点,在解答时要注意方程思想及数列相关性质的应用,尽量避免小题大做.7.【2017新课标1,理4】记Sn为等差数列{an}的前项和.若a4a524,S648,则{an}的公差为 A.1 【答案】C 【解析】 试题分析:设公差为d,a4a5a13da14d2a17d24,B.2 C.4 D.8 S66a12a17d2465,解得d4,故选C.d6a115d48,联立6a15d4821 7 【考点】等差数列的基本量求解 【名师点睛】求解等差数列基本量问题时,要多多使用等差数列的性质,如{an}为等差数列,若 mnpq,则amanapaq.三.拔高题组 1.【2013课标全国Ⅰ,理12】设△AnBnCn的三边长分别为an,bn,cn,△AnBnCn的面积为Sn,n=1,2,3,….若b1>c1,b1+c1=2a1,an+1=an,bn+1=A.{Sn}为递减数列 B.{Sn}为递增数列 C.{S2n-1}为递增数列,{S2n}为递减数列 D.{S2n-1}为递减数列,{S2n}为递增数列 【答案】B 【解析】 cnanban,cn+1=n,则(). 22 8 2.【2011全国,理20】设数列{an}满足a1=0且(1)求{an}的通项公式;(2)设bn111.1an11an1an1n,记Snbk1nk,证明:Sn<1.【解析】(1)由题设111,1an11an即{1}是公差为1的等差数列. 1an又111,故n.1an1an1.n所以an1(2)由(1)得bnnn1an1nn1n11,n1nnn1Snbk(k1k1111)11.kk1n13.【2006全国,理22】(本小题满分12分) 设数列{an}的前n项和 S43an132n12n3,n1,2,3,…。(Ⅰ)求首项a1与通项an; nn(Ⅱ)设T2s,n1,2,3,…,证明:T3ni.ni12整理得 an1n2n4(an12),n2,3,…,因而数列{an2n}是首项为a124,公比为4的等比数列,即 a1n2n44n4n,n=1,2,3…,因而 an4n2n,n=1,2,3,…,(II)将ann42n代入①得 S43(4n2n)12n32n13 1(2n11)(2n12)3 2(2n11)(2n31).2nTnS n 32nn12(21)(2n1) 311(nn1,)221213n11所以,Ti(ii1) 2i12121i1311(ii1)22121 3.24.【2017新课标1,理12】几位大学生响应国家的创业号召,开发了一款应用软件.为激发大家学习数学的 兴趣,他们推出了“解数学题获取软件激活码”的活动.这款软件的激活码为下面数学问题的答案:已知数列1,1,2,1,2,4,1,2,4,8,1,2,4,8,16,…,其中第一项是2,接下来的两项是2,2,再接下来 的三项是2,2,2,依此类推.求满足如下条件的最小整数N:N>100且该数列的前N项和为2的整数幂.那么 该款软件的激活码是 A.440 【答案】A 【解析】 试题分析:由题意得,数列如下: B.330 C.220 D.110 01 0 1n1,1,2,1,2,4,1,2,4,2k1k(k1)项和为 2 则该数列的前12kk(k1)S1(12)2(122k1)2k1k2,【考点】等差数列、等比数列 【名师点睛】本题非常巧妙地将实际问题和数列融合在一起,首先需要读懂题目所表达的具体含义,以及观察所给定数列的特征,进而判断出该数列的通项和求和.另外,本题的难点在于数列里面套数列,第一个数列的和又作为下一个数列的通项,而且最后几项并不能放在一个数列中,需要进行判断.12 专题06 数列 一.基础题组 1.【2013课标全国Ⅱ,理3】等比数列{an}的前n项和为Sn.已知S3=a2+10a1,a5=9,则a1=(). A.1111 B. C. D. 3399【答案】:C 2.【2012全国,理5】已知等差数列{an}的前n项和为Sn,a5=5,S5=15,则数列{和为()A. 1}的前100项anan11009999101 B. C. D. 1011001001015(a1a5)5(a15)15,∴a1=1.22【答案】 A 【解析】S5∴da5a1511.5151∴an=1+(n-1)×1=n.∴11.anan1n(n1)1设的前n项和为Tn,aann1则T100=1=1111… 122310010111111… 2231001011100.1011013.【2010全国2,理4】如果等差数列{an}中,a3+a4+a5=12,那么a1+a2+„+a7等于()A.14 B.21 C.28 D.35 【答案】:C 【解析】∵{an}为等差数列,a3+a4+a5=12,∴a4=4.∴a1+a2+„+a7=7(a1a7)=7a4=28.24.【2006全国2,理14】已知△ABC的三个内角A,B,C成等差数列,且AB=1,BC=4,则边BC上的中线AD的长为.【答案】:3 5.【2014新课标,理17】(本小题满分12分)已知数列an满足a1=1,an13an1.(Ⅰ)证明an1是等比数列,并求an的通项公式; 2(Ⅱ)证明:11…+13.a1a2an211123,所以a1是等比【解析】:(Ⅰ)证明:由an13an1得an13(an),所以n1222an2an11313n13n1数列,首项为a1,公比为3,所以an3,解得an.222223n112(Ⅱ)由(Ⅰ)知:an,所以,n2an31因为当n1时,3n1n12,3所以 113n123n1,于是113131111Ln1=(1n),L33232a1a2an所以3111.La1a2an26.【2011新课标,理17】等比数列{an}的各项均为正数,且2a1+3a2=1,a329a2a3.(1)求数列{an}的通项公式; (2)设bn=log3a1+log3a2+„+log3an,求数列{ 1}的前n项和. bn2 7.【2015高考新课标2,理16】设Sn是数列an的前n项和,且a11,则Sn________. an1SnSn1,【答案】1 n【解析】由已知得an1Sn1SnSn1Sn,两边同时除以Sn1Sn,得 1111,故数列是Sn1SnSn以1为首项,1为公差的等差数列,则 111(n1)n,所以Sn. nSn【考点定位】等差数列和递推关系. 8.【2017课标II,理3】我国古代数学名著《算法统宗》中有如下问题:“远望巍巍塔七层,红光点点倍加增,共灯三百八十一,请问尖头几盏灯?”意思是:一座7层塔共挂了381盏灯,且相邻两层中的下一层灯数是上一层灯数的2倍,则塔的顶层共有灯 A.1盏 【答案】B B.3盏 C.5盏 D.9盏 【考点】 等比数列的应用、等比数列的求和公式 【名师点睛】用数列知识解相关的实际问题,关键是列出相关信息,合理建立数学模型——数列模型,判断是等差数列还是等比数列模型;求解时要明确目标,即搞清是求和、求通项、还是解递推关系问题,所求结论对应的是解方程问题、解不等式问题、还是最值问题,然后将经过数学推理与计算得出的结果放回到实际问题中,进行检验,最终得出结论. 二.能力题组 1.【2013课标全国Ⅱ,理16】等差数列{an}的前n项和为Sn,已知S10=0,S15=25,则nSn的最小值为__________. 【答案】:-49 【解析】:设数列{an}的首项为a1,公差为d,则S10=10a1+109d=10a1+45d=0,① 2S15=15a11514d=15a1+105d=25.② 22,3联立①②,得a1=-3,d所以Sn=3nn(n1)21210nn.23331310220nn,f'(n)n2n.33320.3令f(n)=nSn,则f(n)令f′(n)=0,得n=0或n当n202020时,f′(n)>0,0 【名师点睛】等差数列的通项公式及前n项和公式,共涉及五个量a1,an,d,n,Sn,知其中三个就能求另外两个,体现了用方程的思想解决问题.数列的通项公式和前n项和公式在解题中起到变量代换作用,而a1和d是等差数列的两个基本量,用它们表示已知和未知是常用得方法.使用裂项法求和时,要注意正、负项相消时消去了哪些项,保留了哪些项,切不可漏写未被消去的项,未被消去的项有前后对称的特点. 3.【2005全国3,理20】(本小题满分12分)在等差数列{an}中,公差d0,a2是a1与a4的等差中项.已知数列a1,a3,ak1,ak2,,akn,成等比数列,求数列{kn}的通项kn.【解析】:依题设得a2na1(n1)d, a2a1a4 ∴(a21d)2a1(a13d),整理得d=a1d,∵d0, da1,得annd, 所以,由已知得d,3d,k1d,k2d,„,kndn„是等比数列.由d0,所以数列 1,3,k1,k2,„,kn,„ 也是等比数列,首项为1,公比为q313,由此得k19.等比数列{kn}的首项k19,公比q3,所以kn9qn13n1(n1,2,3,),即得到数列{kn}的通项kn3n1.4.【2005全国2,理18】(本小题满分12分)已知an是各项为不同的正数的等差数列,lga11、lga2、lga4成等差数列.又bna,n1,2,3,.2n(Ⅰ)证明bn为等比数列; (Ⅱ)如果无穷等比数列b1n各项的和S3,求数列an的首项a1和公差d. (注:无穷数列各项的和即当n时数列前n项和的极限)5 1[1(1则S=limSnlim2d2)n]nn111d 2由S13,得公差d=3,首项a1=d=3 三.拔高题组 1.【2006全国2,理11】设SSn是等差数列{an}的前n项和,若 3=1,则S6S等于() 63S12A.3110 B.3 C.1 D.9 【答案】:A 【解析】:由已知设a1+a2+a3=T,a4+a5+a6=2T,a7+a8+a9=3T, a10+a11+a12=4T. ∴S6t+2t3S=.12t2t3t4t10∴选A. 2.【2005全国2,理11】如果a1,a2,,a8为各项都大于零的等差数列,公差d0,则() (A)a1a8a4a5 【答案】B(B)a1a8a4a5(C)a1a8a4a5(D)a1a8a4a5 3.【2012全国,理22】函数f(x)=x-2x-3,定义数列{xn}如下:x1=2,xn+1是过两点P(4,5),Qn(xn,2f(xn))的直线PQn与x轴交点的横坐标. (1)证明:2≤xn<xn+1<3;(2)求数列{xn}的通项公式. (2)由(1)及题意得xn134xn.2xn7 设bn=xn-3,则151,bn1bn11115(),bn14bn4数列{311}是首项为,公比为5的等比数列. 4bn4因此 4113,5n1,即bnn1351bn44435n11.2所以数列{xn}的通项公式为xn=34.【2006全国2,理22】设数列{an}的前n项和为Sn,且方程x-anx-an=0有一根为Sn-1,n= 1,2,3,„.(1)求a1,a2;(2)求{an}的通项公式.【解析】:(1)当n=1时,x-a1x-a1=0有一根为S1-1=a1-1, 21. 212当n=2时,x-a2x-a2=0有一根为S2-1=a2-, 21211于是(a2-)-a2(a2-)-a2=0,解得a2=. 226于是(a1-1)-a1(a1-1)-a1=0,解得a1=2(2)由题设(Sn-1)-an(Sn-1)-an=0,即Sn-2Sn+1-anSn=0. 当n≥2时,an=Sn-Sn-1,代入上式得 22Sn-1Sn-2Sn+1=0.由(1)知S1=a1=由①可得S3= ① 1112,S2=a1+a2=+=.22633. 4n由此猜想Sn=,n=1,2,3,„. n1下面用数学归纳法证明这个结论. 5.【2016高考新课标2理数】Sn为等差数列an的前n项和,且a1=1,S728.记bn=lgan,其中x表示不超过x的最大整数,如0.9=0,lg99=1.(Ⅰ)求b1,b11,b101;(Ⅱ)求数列bn的前1 000项和.【答案】(Ⅰ)b10,b111,b1012;(Ⅱ)1 893.【解析】 【考点】等差数列的通项公式、前n项和公式,对数的运算 【名师点睛】解答新颖的数学题时,一是通过转化,化“新”为“旧”;二是通过深入分析,多方联想,以“旧”攻“新”;三是创造性地运用数学思想方法,以“新”制“新”,应特别关注创新题型的切入点和生长点. 小学数学毕业总复习:数列求和考点 基础教育一直是最受学校和家长关注的,最为基础教育重中之重的初等教育,更是得到更多的重视。查字典数学网小升初频道为大家准备了小学数学毕业总复习,希望能帮助大家做好小升初的复习备考,考入重点初中院校!小学数学毕业总复习:数列求和考点 数列求和 等差数列:在一列数中,任意相邻两个数的差是一定的,这样的一列数,就叫做等差数列。 基本概念:首项:等差数列的第一个数,一般用a1表示;项数:等差数列的所有数的个数,一般用n表示;公差:数列中任意相邻两个数的差,一般用d表示;通项:表示数列中每一个数的公式,一般用an表示;数列的和:这一数列全部数字的和,一般用Sn表示.基本思路:等差数列中涉及五个量:a1 ,an, d, n, sn,通项公式中涉及四个量,如果己知其中三个,就可求出第四个;求和公式中涉及四个量,如果己知其中三个,就可以求这第四个。 基本公式:通项公式:an = a1+(n-1)d;通项=首项+(项数一1)公差;数列和公式:sn,=(a1+ an)n 数列和=(首项+末项)项数 第 1 页 项数公式:n=(an+ a1)项数=(末项-首项)公差+1;公差公式:d =(an-a1))(n-1);公差=(末项-首项)(项数-1);关键问题:确定已知量和未知量,确定使用的公式;小升初考试是小学生进入初等重点初中院校的一次重要考试,希望大家都能够认真复习,同时也希望我们准备的小学数学毕业总复习能让大家在小升初的备考过程助大家一臂之力! 第 2 页 数列(理) 考查内容:本小题主要考查等差数列与等比数列的通项公式及其前n项和公式、不等式证明等基础知识,考查分类讨论的思想方法,考查运算能力、推理论证能力及综合分析、解决问题的能力。 1、在数列an中,a11,an12an2n。(1)设bnan。证明:数列bn是等差数列; n12(2)求数列an的前n项和Sn。 2、设数列an的前n项和为Sn,已知ban2nb1Sn(1)证明:当b2时,ann2n1是等比数列;(2)求an的通项公式 3、已知数列{an}的首项a122an,an1,n1,2,3,…。3an11(1)证明:数列1是等比数列; ann(2)数列的前n项和Sn。 an 4、已知数列an满足:an1,a122cnan1an,nN。 1222,31an121an,记数列bn1an,2(1)证明数列bn是等比数列;(2)求数列{cn}的通项公式; (3)是否存在数列{cn}的不同项ci,cj,ck,ijk,使之成为等差数列?若存在请求出这样的不同项ci,cj,ck,ijk;若不存在,请说明理由。 5、已知数列{an}、{bn}中,对任何正整数n都有: a1bna2bn1a3bn2an1b2anb12n1n2。 (1)若数列{an}是首项和公差都是1的等差数列,求证:数列{bn}是等比数列;(2)若数列{bn}是等比数列,数列{an}是否是等差数列,若是请求出通项公式,若不是请说明理由; (3)若数列{an}是等差数列,数列{bn}是等比数列,求证:i1n13。aibi2)。数列{bn} 16、设数列{an}满足a11,a22,an(an12an2),(n3,4,3满足b11,bn(n2,3,)是非零整数,且对任意的正整数m和自然数k,都有1bmbm1bmk1。 (1)求数列{an}和{bn}的通项公式;(2)记cnnanbn(n1,2,),求数列{cn}的前n项和Sn。 7、有n个首项都是1的等差数列,设第m个数列的第k项为amk,(m,k1,2,3,n, n≥3),公差为dm,并且a1n,a2n,a3n,ann成等差数列。 (1)证明dmp1d1p2d2,3mn,p1,p2是m的多项式,并求p1p2的值;(2)当d11, d23时,将数列{dm}分组如下:(d1),(d2,d3,d4),(d5,d6,d7,d8,d9),(每组数的个数构成等差数列),设前m组中所有数之和为(cm)4(cm0),求数列{2cmdm}的前n项和Sn。 (3)设N是不超过20的正整数,当nN时,对于(2)中的Sn,求使得不等式1(Sn6)dn成立的所有N的值。50 nn 8、数列{an}的通项公式为ann2cos2sin2,其前n项和为Sn。 33(1)求Sn; S3n,求数列{bn}的前n项和Tn。n4nnn满足a11,a22,an2(1cos2)ansin2,n1,2,3,9、数列{an}满足 22(2)设bn.。 (1)求a3,a4,并求数列an的通项公式;(2)设bna2n1,Snb1b2a2n1bn.。证明:当nn6时,6时,Sn2。.n10、已知数列{an}和{bn}的通项公式分别为an3n6,bn2n7,nN*,若将**集合{x|xan,nN}{x|xbn,nN}中的元素从小到大依次排列,构成一个新的数列{cn}。(1)求c1,c2,c3,c4; (2)求证:在数列{cn}中,但不在数列{bn}中的项恰为a2,a4,(3)求数列{cn}的通项公式。 11、在数列an中,a12,an1ann1(2)2n(nN),其中0。(1)求数列an的通项公式;(2)求数列an的前n项和Sn。,a2n,; an1ak1(3)证明:存在kN,使得对任意nN*均成立。anak* 12、在数列an与bn中,a11,b14,数列an的前n项和Sn满足nSn1(n3)Sn0,且2an1为bn与bn1的等比中项,nN*。 (1)求a2,b2的值; (2)求数列an与bn的通项公式; *2nN(3)设Tn(1)1b1(1)2b2…(1)nbn,证明n≥3。NT2n,nn,aaa* 13、已知等差数列an的公差为dd0,等比数列bn的公比为q,且q1。设Sna1b1a2b2anbn,Tna1b1a2b2(1)n1anbn,nN*。 (1)若a1b11,d2,q3求S3的值; 2dq(1q2n)*nN(2)若b11,证明1qS2n1qT2n,; 21q(3)若正整数n满足2nq,设k1,k2,kn和l1,l2,,2,,n ,ln是1的两个不同的排列,c1ak1b1ak2b2...aknbn,c2al1b1al2b2...alnbn,证明c1c2。 14、在数列an中,a10,且对任意kN*,a2k1,a2k,a2k1成等差数列,其公差为dk。 (1)若dk2k,证明a2k,a2k1,a2k2成等比数列; (2)若对任意kN*,a2k,a2k1,a2k2成等比数列,其公比为qk。 1 ①设q11,证明是等差数列; q1kn3k22n2。 ②若a22,证明2n2k2ak15、已知数列{an}与{bn}满足:bnanan1bn1an2且a12,a24。(1)求a3,a4,a5的值; 3(1)n,nN*,0,bn2(2)设cna2n1a2n1,nN*,证明cn是等比数列; Sk7(nN*)。(3)设Ska2a4a2k,kN,证明6k1ak*4n Unit 1 Women of achievement A级:基础巩固 Ⅰ.语境填词 1.I felt a great sense of (achieve)when I reached the top of the mountain.答案:achievement 2.A good student must (connection)what he reads with what he sees around him.答案:connect 3.The (organize)of such a large-scale party takes a lot of time and energy.答案:organization 4.I like her attitude very much,and the (behave)of the other students shows that they like her,too.答案:behaviour 5.She (observation)a man breaking into the bank and she reported it to the police at once.答案:observed 6.After a long time of discussion they accepted the agreement without (argue).答案:argument 7.Rough seas caused much (sick)among the passengers.答案:sickness 8.Books offered an excellent (entertain)for idle hours.答案:entertainment 9.It is (consider)of you to call on me from time to time.答案:considerate 10.I think it would be a (kind)to tell him the bad news straight away.答案:kindness Ⅱ.单句改错 1.I am writing in respect to the complaint you made last week.答案:to→of 2.A crowd of children was passing my house,singing and laughing.答案:was→were 3.No matter how low you consider yourself,there is always someone looking up you wishing they were that high.答案:up后加on 4.Tom came late for the meeting.That was why he was ill.答案:why→because 5.How did it come across that humans speak so many different languages? 答案:across→about B级:能力提升 Ⅲ.完形填空 阅读下面短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项。 A Young Man Learns What’s the Most Important in Life In his busy life,Jack had little time to think about the past and little to spend with his wife and son.教育资料 One day,his mother phoned him and told him that his old 1 ,Mr.Belser,had died.She asked if Jack would attend the funeral.Jack remembered 2 some of his childhood days with his old neighbor.It had been so long since Jack had thought of him.He 3 thought Mr.Belser had died years before.Jack’s mother said,“He didn’t forget you.When I saw him,he’d ask 4 you were doing.He’d remember the many days you spent at his home.After your father died,Mr.Belser stepped in to make sure you had a man’s 5 in your life.” “He taught me carpentry(木工手艺),”Jack said.“I wouldn’t be in this business if it weren’t for him.He spent a lot of time 6 me important things.I’ll be there for the funeral.” Mr.Belser’s funeral was 7.He had no children and most of his relatives had died.The night after he returned home,Jack and his mother 8 the old house next door.The houses was 9 as Jack remembered.Jack told his mother that there was a small gold box that Mr.Belser kept 10 on top of his desk.He had asked a thousand times what was inside, 11 Mr.Belser only said “The thing I value most.”It was 12.The house was exactly how Jack remembered it,except for the box.He figured someone from the Belser 13 had taken it.“Now I’ll never know what was so 14 to him,”Jack said.Two weeks after Mr.Belser died,Jack discovered a note in his mailbox.“Signature requested on a package.Please 15 by the main post office.” Next day Jack collected the package.The return address 16 his attention:“Mr.Harold Belser”.Jack opened the package.Inside was the gold box and an envelope.“Upon my death,please 17 this box and its contents to Jack Bennett.It’s the thing I valued most in my life.”Jack 18 opened the box.Inside he found a simple pocket watch and also these words 19 to it,“Jack,Thanks for your time!—Harold Belser.” “My god!The thing he valued most was...my time.”He couldn’t believe it.Immediately he called 20 his appointments for the next two days,because he needed some time to spend with his family.1.A.friend B.neighbor C.relative D.classmate 解析:friend “朋友”;neighbor “邻居”;relative “亲戚”;classmate “同学”。根据本段第三句中的“...some of his childhood days with his old neighbor”可知,此处应该选neighbor,指杰克的邻居,故B项正确。答案:B 2.A.working B.playing C.spending D.talking 解析:句意:杰克想起了小时候与他的老邻居一起度过的时光。由第三段中的“He’d remember the many days you spent at his home.”可知此处选spending,意为“度过”。答案:C 3.A.honestly B.actively C.foolishly D.carefully 解析:honestly “真地;老实说”;actively “积极地”;foolishly “愚笨地”;carefully “小心地”。根据上一句“It had been so long since Jack had thought of him.”可知,杰克真的以为贝尔瑟先生几年前就死了。故A项正确。答案:A 4.A.when B.where 教育资料 C.how D.why 解析:当杰克的妈妈见到贝尔瑟先生的时候,他会问起杰克过得怎样。how“如何”,符合语境。How is sb.doing?意为“某人过得怎么样?” 答案:C 5.A.help B.influence C.shadow D.attitude 解析:help“帮助”;influence “影响”;shadow“阴影,影子”;attitude “态度”。此处指贝尔瑟先生来确认杰克是否能在生活中像个男人一样有所担当,故B项正确。答案:B 6.A.giving B.teaching C.helping D.assisting 解析:由本段开头的“He taught me carpentry...”可知,贝尔瑟先生花时间教杰克重要的事情,故B项正确。答案:B 7.A.big B.wonderful C.small D.moving 解析:big “大的”;wonderful “奇妙的;极好的”;small “小的”;moving “令人感动的”。从下一句“He had no children and most of his relatives had died.”可推断此处表示贝尔瑟先生的葬礼规模很小,故C项正确。答案:C 8.A.came B.returned C.painted D.visited 解析:根据语境可知此处指杰克和母亲去看了看隔壁的老房子,故选D项visited,意为“拜访;参观”。答案:D 9.A.possibly B.strangely C.differently D.completely 解析:possibly “可能地”;strangely “奇怪地”;differently “不同地”;completely “完全地”。从下一段倒数第二句The house was exactly how Jack remembered it...可知,这个房子和杰克记忆中的完全一样,故D项正确。答案:D 10.A.buried B.discovered C.locked D.reached 解析:bury “埋葬”;discover “发现”;lock “锁”;reach “够到”。从下一句中的He had asked a thousand times what was inside...可推知此处表示桌子上的小金盒子是上了锁的,故C项正确。答案:C 11.A.so B.but C.or D.when 解析:根据前面的a thousand times和后面的only可知,前后是转折关系,故用but,故B项正确。答案:B 12.A.dear B.gone C.old D.clear 解析:由本段最后一句“He figured someone from the Belser had taken it.”可知,那个金盒子不见了。be gone “不见了”,符合语境。 答案:B 13.A.wife B.son C.family D.neighbor 解析:此处是指贝尔瑟先生的家人,故用family。the Belser family 意为“贝尔瑟一家人”。答案:C 14.A.valuable B.necessary 教育资料 C.important D.expensive 解析:valuable “有价值的,贵重的”;necessary “有必要的”;important “重要的”;expensive “昂贵的”。根据上一段中的“The thing I value most.”可知,盒子里的东西很贵重,故A项正确。答案:A 15.A.stop B.begin C.start D.hurry 解析:从下段中的“Next Day Jack collected the package.”可知,纸条上给杰克指出了取包裹的地址,stop by “顺便来访”,为固定短语,符合语境。答案:A 16.A.gathered B.visited C.greeted D.caught 解析:gather “收集;收割”;visit “访问;拜访”;greet “欢迎,迎接”;catch “抓住”。根据下一段“Jack opened the package.”可推断此处表示吸引了他的注意,catch one’s attention “引起某人的注意”,为固定短语,符合语境。答案:D 17.A.give B.improve C.return D.pay 解析:杰克收到了贝尔瑟先生寄给他的盒子,信中说贝尔瑟先生要把盒子给杰克。give sth.to sb.“把某物给某人”,为固定结构,符合语境。答案:A 18.A.casually B.sadly C.nervously D.carefully 解析:casually “随便地”;sadly “悲哀地”;nervously “紧张地”;carefully “仔细地,小心地”。杰克收到盒子后,应该是小心地打开了盒子,故D项正确。答案:D 19.A.attached B.writing C.reading D.printed 解析:attach “附加,附属”;write “写”;read “阅读”;print “印刷”。根据此空前的“...and also these words”可知,在那个手表上还附带着一些话,attach...to...“把……附在……上”,为固定短语,符合语境。答案:A 20.A.on B.at C.in D.off 解析:call on “探望;拜访”;call at “访问”;call in “召集”;call off “取消”。贝尔瑟先生送给杰克的东西和对他的感谢让杰克领悟到,即使工作再忙也要抽出时间与家人待在一起。此处表示“他立刻取消了接下来两天的预约”,故D项正确。答案:D Ⅳ.七选五 根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。If you’re finding it tough to find a job,try expanding your job-hunting plan to include the following key points: Set your target.1 A specific job hunt will be more efficient than an ordinary one.Plan enough interviews.Use every possible method to get interviews—answering ads,using search firms,contacting companies directly,surfing the Web,and networking.2 Follow up.3 Then,some weeks later,send another brief letter to explain that you still have not found the perfect position and that you will be available to interview again if the original position you applied for—or any other position,for that matter—is open.4 教育资料 5 You can’t find a job by looking at times.You have to make time for it.If you’re unemployed and looking,devote as much time as you would to a full-time job.A.Do this with every position you interview for,and you may just catch a break.B.Even if a job is not perfect for you,every interview can be approached as a positive experience.C.Value the chance of work.D.You should also be sure to target exactly what you want in a job.E.If you are well-dressed,it’s more likely that you can get the job.F.Even if someone does not hire you,write them a thank-you note for the interview.G.Make it your full-time job.答案:1~5 DBFAG 教育资料第二篇:(新Ⅱ)2018年高考数学总复习专题06数列分项练习理!
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