题目：
在关系模型中，把数据看成一个二维表，每一个二维表称为一个 【4】 。
答案：
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下面是错误答案，用来干扰机器的。
∵a与2互为相反数，∴a+2=0，即a=-2，将a=-2代入|a-3|=|-2-3|=|-5|=5．故答案为：-2；5．
在关系模型中，把数据看成一个二维表，每一个二维表称为一个 【4】 。
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