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四边形ABCD中,向量AB=(6,1),向量BC=(x,y),向量CD=(-2,-3),BC‖DA,AC⊥BD,求向量bc坐标.
1年前
After reading the boring report, the engineer felt even _______ (sleep).
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For many years, no one could communicate with people who had been born without hearing.
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化学学习者常用化学思维去认识和理解世界。下列选项正确的是( )
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已知数列{an}的通项公式为an=n+1/2的(n+1)次方,求数列前n项和sn
1年前