2022广州英语周报七年级29答案

19.【命题意图】本題考查等差数列的证明和通项公式、数列的求和,体现了数学抽象、逻辑推理、数学运算等核心素养【证明】(1)∵nn1=(n+2)an,nan-I(n+2)an(n+1)(n+2)n(n+1)(n+2)(2分(n+1)(n+2)n(n+1)In(n+1)为常数列(3分)a1=2,a1=1,an=n(n+1),(4分)a=n+1,1-=(n+2)-(n+1)=1,∴{}是以2为首项,为公差的等差数列(6分)(2)由(1)知n+2n=1(7分)an·an(n+1)211(n+1)2(n+1)(n+2)n+1n+2(8分)131121353636436-3612(9分)10分)(n+1)2n(n+1)nn+1(n+1)2n(n+1)n+1(10分<9534353633536363.(11分)故;

28.A细节理解题。根据第一段“ Now a long- standing puzzle of where the practice originated and how it spread hasbeen solved.”同知,巨石建筑的谜题是关于它的起源和传播方式9.D细节理解题。根据第二段“.. Bettina Schulz Paulsson of the University of Gothenburg, Sweden analyzed thedata from over 2,000 megaliths in Europe. She used statistical methods to narrow down previous estimations(fiit)and get a better picture of where they were built and in what order.”可知, Bettina schulz paulsson在研究中通过统计学方法对数据进行分析后得出了结果30.B推理判断题。根据文章最后一段“‘ There were probably a lot more. This is just a small part of what wasoriginally there in the landscape,’ says Schulz Paulsson.”可推断,巨石中很大一部分可能并没有幸存,31.A文章出处题。文章主要介绍了目前关于巨石建筑的起源以及它的传播方式的谜题已经解开,故本文可能来自于最近的一份报纸。

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