2022 英语周报 九年级 新目标 50答案

第二节书面表达【写作指导】本篇书面表达要求考生写一封邮件。根据题目要求可知,时态应以一般现在时和一般将来时为主,现在进行时为辅;人称以第一人称为主。邮件中定要囊括题目要求中所给出的两个要点:目前的学习状况和考试结束后想要去旅行的地点及原因。内容可适当扩充,不要逐条翻译要点,注意过渡词的灵活使用,同时可多运用一些高级词汇和句式,以提高作文的得分档次。One possible versionDear peterI am glad to receive your letter. Thanks for yourconcern about my recent learning status and my travelarrangements after the college entrance examination, which Iwill explain respectively as below.With the examination drawing near, I am now fulldevoted to my study in the hope of making myself admitted tomy dream university. As for the travel plan after the examI'm considering touring around Beijing. Not only is it anamazing city with varieties of tourist attractions, but also it ishome to many top universities, which fascinates me a lotThanks again for your concern about me. Wish me goodluck in the exam!天LiH

18.解:(1)设等比数列{an}的公比为q,由已知an+1=2S+2,可得=2S1-1+2(m≥2),两式相减可得an+1-an=25-251分即an+1-an=ga、整理得an+1=3an,可知q=3,…2分已知a+1=2S+2,令n=1,得a2=2a1+2,即a1q=2a1+2,解得a1=2,3分故等比数列{an)的通项公式为an=2·3(n∈N);4分由b1=2,(n+2)=m,(n∈N”)得一22,那么一号,一是一…一m2,一m以上m个式子相乘,可得一××号“2n+1n(n+1)b=n(n+1)(n≥2)5分又b1=2满足上式,所以(b。)的通项公式b=n(n+1)(n∈N).……6分(2)若在a。与an+1之间插入n个数,使这n+2个数组成一个公差为cn的等差数列,则a+1-an=(n+1)cn,……7分即为2,3-2·3=(m+1),整理得,1,所以b。=4,n3…,………………………………9分T=b1+b2C2+b23+…+b-c4+b=4·1·3+4·2·32+4·3·32+…+4·(n-1)3-2+4·n·3-1=4(1·3°+2·32+3·32+…+(n-1)32+n·3-1)3T=4[1·32+2·32+…+(n-1)3+n3],10分两式相减得:2T=4(3+3+·32所以=2(m,3+12x)=1+(2n-1)(m∈N).…分

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