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I didn't see your sister at the meeting. If she _____, she would have met my brother. [ ]
1年前
在四边形ABCD中,向量AB=(6,1),向量CD=(-2,-3),BC//DA,AC垂直BD,求向量BC的坐标
1年前
Researchers have found that there are some basic things that you can do to become happier.
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1年前
若a-1的绝对值与(b+2)的2次方互为相反数,试求(a+b)的2009次方+a的2010
1年前