已知a、b互为倒数，c、d互为相反数，且m的绝对值为1，求：2ab-m2-3c+

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问题解答题

已知a、b互为倒数，c、d互为相反数，且m的绝对值为1，求：2ab-m2-

3c+3d

的值．

答案

根据题意得ab=1，c+d=0，m=±1，

当m=1时，原式=2×1-1²-

3×0

5×1

=1；

当m=-1时，原式=2×1-（-1）²-

3×0

5×(-1)

=1，

所以2ab-m2-

3c+3d

的值为1．

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短文改错。

该短文中共有10处错误，每句中最多有两处，错误涉及一个单词的增加、删除或修改。

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Today we went to climb the West Hill. Early in morning we started out and arrived an hour late.

Then we began to climb. The hill was high and some of us got tired soon, and all of us were very

excited. We cheered happily when we got the top. We had our lunch there and had enjoyed ourselves

very much. Unfortunate, when we walked down the hill, we were caught by a rain. We remained

calmly, shared umbrellas and raincoats and walked carefully. Finally we both reached the parking lot

safely. In spite of the unexpecting rain and wind, we had a good time.

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