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关于一个高数的旋转体体积的题有X^2+Y^2≤2x和y≥x组成的图形绕x=2绕一圈的体积 其中有个选项是2π∫{0,1} (2-x)[(2x-x^2)^1/2-x]我觉得这个是对的可是答案不是这个,这个正确吗 等比数列{an}的公比为-1/2,前n项和Sn,满足limSn=1/a1,则首项a1 已知由正数组成的数列an前n项和为Sn若a1=1/2,且n为Sn与1/an的等比中项.求limSn Dogs can guard our homes .改为一般疑问句 Dogs help ___ our homework.They're our friends.A.guard B.watch C.look D.forget With the fence_________,the cattle can be kept_______the garden.A.putting up; out of B.being added to ;away from C.built ;out of D.being add to; away from.说明为什么选这个,为什么不选那个.感激不尽! 英语独立主格结构The story impressing me so much,I want to keep it in mind.这句话用独立主格结构有没有语法错误? Hello,I'm busy now,wait in touch with you! 一篇600字的作文,题目是《他也很重要》,要求必须要用借物抒情.比如说母爱或者是友谊什么的.速度我很急如题,很急很急啊.速度啦,谢谢啊不要老师的！！！ 设数列{an}的前n项和为Sn,已知A1=a,An+1=Sn+3^n（三的n次方）,n∈N*08年全国高考2卷理科数学20题：设数列{an}的前n项和为Sn，已知A1=a，An+1=Sn+3^n（三的n次方），n∈N*设bn=Sn-3^n，求数列{bn}的通项公式 怎么很快的背一篇语文课文,我们要背朱自清写的《春》,好多啊,老师只给了我们几天时间背,怎么背啊 You need more practice underwater before you can start this mission 在Gta SanAndreas里有一句英文字我看不懂就是“You need more practice underwater before you can start 什么来的,请大家帮我解开…… but even that is not very common什么意思 Hardly had he heard his name____________when he saw an old friend of his _____________behind him,saving his hand to him.A.call;sat B.called ; seating C.calling; sit D.called; seated.说明为什么选这个,为什么不选那个.感激不尽! 关于毛主席的事例有? Have a look the picture 哪里有错 When I passed the playground,I saw some students _____ football.A play B playing C to play D to playing 在等比数列{an}中,前n项之和Sn满足limSn=7,那么a1的取值范围是______希望过程能详细一些~~谢谢~~ Sn是无穷等比数列{an}前n项和, limSn=4,则首向a1的取值范围 正项无穷等比数列an的前n项和为Sn,limSn=1/3,求a1的取值范围? ()The boss is too busy now to ______ a minute to talk with you.A.giveB.spareC.attractD.bring talk to u later See u even worse和out-of-date if you surf the internet,you will be surprised to see quite a few sites that are even out of date.4157 He worked____________manner to complete his project that he did not even stop for a break.A.with such a diligent B.by a such diligent C.in such a diligent D.with a such diligent.说明为什么选这个,为什么不选那个.感激不尽! 麻烦翻译下Thank you for your email of Jan 23, 2008 offering us 50 tons of first-class coffee at US$5Thank you for your email of Jan 23, 2008 offering us 50 tons of first-class coffee at US$500 per ton CIF New York Do you know the girl who often help her classmates哪错了这句话 哪里错了 detroyed是什么意思?和 Even the date-September 11,2001- has meaning to most Americans的译文 even the date --september11 ,2001--has meaning to most Americans为什么has不变had why does the date september 11 2001 have meaning to most Americams 老师出的问题, exp.date 01 30 09 是到2009年1月30 ;还是到2001年9月30好是美国的写法.