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问题 选择题
矩形ABCD中的顶点A、B、C、D按顺时针方向排列，若在平面直角坐标系内，B、D两点对应的坐标分别是（2，0）、（0，0），且A、C两点关于x轴对称，则C点对应的坐标是（　　）
A．（1，1）B．（1，-1）C．（1，-2）D．（
2
，-
2
）
答案

已知B，D两点的坐标分别是（2，0）、（0，0），

∴OB=2，

连接AC，因为A、C两点关于x轴对称，所以AC⊥BD，

所以四边形ABCD为正方形，

即可知A坐标为（1，1），

所以点C坐标为（1，-1）．

故选B．

完形填空

The Internet has become part of young people’s life. _1. _______ report shows that 38% of students often use the Internet. Most of them get _2.________ (use) information on the Internet _3._______ use the Internet to help with their studies. But many students don’t use it _4.________ a good way. Some play games too much, and some visit websites __5.__________ shouldn’t look at. So bad things may happen __6._________ students spend too much time on the Internet.

__7._______ is important for students to use the Internet properly. Now we have a textbook, __8._______ uses many examples to teach students some good ways to use the Internet. It gives useful __9._______(advise).

Some students also make friends on the Internet. But if you want to have a face-to-face _10.__ ______ (meet) with your online friends, please let your parents know and meet in a proper place.
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填空题
把下列代数式的字母代号填人相应集合的括号内：
A．xy+1     B．-2x2+y     C.-
xy2
3
      D.-4
1
2
      E.-
1
x
    F．x4 G.
1
8
x3-2ax2-x     H．x+y+z     I.
2005
ab
-3J.
1
3
(x+y)     K.2ab+
3
c

（1）单项式集合　{______}
（2）多项式集合  {______}
（3）三次多项式  {______}．
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