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在方向水平的匀强电场中，一不可伸长的不导电细线的一端连着一个质量为m的带电小球，另一端固定于O点。把小球拉起直至细线与电场线平行，然后无初速释放。已知小球摆到最低点的另一侧，线现竖直方向的最大夹角为θ，如图。求小球经过最低点时细线对小球的拉力。从释放点到左侧最高点，据动能定理得 ... 全文
2010-12-27 23:01 来自版块 -
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In Britain. Packets of cigarettes come with a government health warning ___to them.A attaches B to attach C attaching D attached这句啥意思阿。
2010-10-14 18:15 来自版块 -
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--w'd like a standard room, please.--I'm sorry. All but two single rooms with Internet access ____.A were reserved B has been rese... 全文
2010-10-14 18:12 来自版块 -
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-Thanks for you help.but can you do me one more favor,please?-_____,sir. what's then?A Just a minute B My pleasure C That's right... 全文
2010-10-14 18:10 来自版块 -
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China’s New Food Act provides for a food recall system______to producers have to stop production_____their food isn’t up to standards. A．tha... 全文
2010-10-12 21:47 来自版块 -
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--Do you feel like walking to the cinema or__we take a bus?--I'd like to walk .But since there isn't much time left,I'd rathe... 全文
2010-10-12 21:45 来自版块 -
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Nearly half a million people are believed _________their homes as a result of the disaster. A．to leave B．to be left C．to be leaving... 全文
2010-10-12 21:41 来自版块 -
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- -这个是初中的几个词，不过我还是没弄懂。(1)take spare speng pay.(2)award present prize reward
2010-09-27 12:30 来自版块 -
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During the period of recent terrorist activities,people____not to touch any unattended bag.A had always been warned B w... 全文
2010-09-27 12:28 来自版块 -
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The employees_____that they should renew their contracts within a week.A advise B have advised C are advised D had been advised这个要怎么选。这句话什么... 全文
2010-09-27 12:25 来自版块 -
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这个w是怎么转成除式的形式的? - -老师转化这步给个详解~
2010-09-27 00:54 来自版块 -
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It is _____the customers' needs that has made chain stores so popular in big cities in china .A meeting B met C to have meet ... 全文
2010-09-23 18:08 来自版块 -
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老师都说要把知识点串联起来。但是要怎么做啊?比方说向量和立体几何，怎么样才叫把他们串联起来?
2010-09-20 21:44 来自版块 -
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求分析。~这样看的到图咩 0 0
2010-09-18 21:29 来自版块 -
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[图片]物质的量同类题，不知道怎么分析。
2010-09-17 00:58 来自版块 -
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已知f(-x)=f(x),f(2+x)=-f(2-x),求这个函数的周期。f(-x)=f(x)，说明是个偶函数，用x代替-x，求出关于(2,0)中心对称。然后怎么办啊 = =。完全不懂。
2010-08-03 19:00 来自版块 -
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设函数 f(x)=ax^3-3x+1(x∈R)，若对于任意的x∈[-1,1] 都有f(x)≥0 成立，则实数a的值为___。 我求出来是a≤4，错了。不懂ing..
2010-07-31 19:16 来自版块 -
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老师 - -为什么不要考虑空集的情况?我纠结一上午了我
函数f（x）=lg（x^2-x-2）的定义域为集合A，若C={x|4x+p＜0}，C包含于A，求实数p的取值范围。
2010-07-06 09:55 来自版块 -
