下列分式中，无论x为何值，一定有意义的是（） A．x-1x+1 B_爱下问搜题

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问题选择题

下列分式中，无论x为何值，一定有意义的是（　　）

A．

x-1

x+1

B．

x-1

x

C．

x+1

x2-1

D．

x-1

x2+1

答案

A、当x+1=0，即x=-1时，分式

x-1

x+1

的分母为零，所以该分式无意义；故本选项错误；

B、当x=0时，分式

x-1

x

的分母为零，所以该分式无意义；故本选项错误；

C、当x=±1时，分式

x+1

x2-1

的分母为零，所以该分式无意义；故本选项错误；

D、

x-1

x2+1

中，无论x为何值，分母x²+1≠0，所以该分式有意义；故本选项正确；

故选D．

完形填空

短文填词根据文章意思和首字母提示写出所缺单词，每空一词（满分10分，每小题1分）。

George Stephenson is my f 小题1: inventor. He was b 小题2: in 1781. He was f 小题3: a poor English worker's family. His father was too poor to s 小题4: him to school. He began l 小题5: his ABC when he was seventeen. On his 18th birthday he could write his o 小题6: name.

George had to work when he was o 小题7: a small child. He worked twelve h 小题8: every day. But he worked and studied very h 小题9: . As he studied hard, he invented many things. The locomotive（火车头）was the g 小题10: one among them.

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