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问题 解答题

化简下列各式：

（1）-（x+y）+（3x-7y）；                 （2）（4a2-3b2）-[2（a2-1）+2b2-3]

答案

（1）原式=-x-y+3x-7y，

=2x-8y；

（2）原式=4a2-3b2-[2a2-2+2b2-3]，

=4a2-3b2-2a2+2-2b2+3，

=2a2-5b2+5．

单项选择题

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A．table

B．tree

C．control

D．event
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A．引流管有阻塞
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C．呼吸道不通畅
D．肺膨胀良好
E．并发支气管胸膜瘘
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