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问题 选择题

下列函数中，二次函数是（　　）

A．y=（m2+1）x2

B．y=x2-x（x-2）

C．y=ax2+bx+c

D．y=x+1

答案

A、不论m取什么实数，m2+1≠0，正确；

B、y=x2-x（x-2）=2x，正比例函数，错误；

C、y=ax2+bx+c，没有强调a≠0，不能确定为二次函数，错误；

D、y=x+1，一次函数，错误．

故选A．

改错题

文中共有10处错误，每句中最多有两处。

增加：在缺词处加一个漏词符号（^），并在此符号下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1．每处错误及其修改均仅限一词。2．只允许修改10处，多者（从第11处起）不计分。

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填空题

GB1576—2001《工业锅炉水质》标准指出，如测定溶解固形物有困难时，可采用测定（）或（）的方法来间接控制。
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