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问题 填空题
设定义域为R的函数f(x)=
|lgx|，x＞0
-x2-2x，x≤0
，则函数f（x）的零点为______．
答案

∵定义域为R的函数f(x)=

|lgx|，x＞0
-x2-2x，x≤0
， 由
lgx=0
x＞0
，或 
-x2-2x=0
x≤0
，可得

x=1，或 x=0 或x=-2，则函数f（x）的零点为-2，0，1，

故答案为-2，0，1．

问答题 简答题

阀门控制方式的转换步骤有哪些？
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单项选择题

To Err is Human


by Lewis Thomas
Everyone must have had at least one personal experience with a computer error by this time. Bank balances are suddenly reported to have jumped from $ 379 into the millions, appeals for charitable contributions are mailed over and over to people with crazy sounding names at your address, department stores send the wrong bills, utility companies write that they’re turning everything off, that sort of thing. If you manage to get in touch with someone and complain, you then get instantaneously typed, guilty letters from the same computer, saying, "Our computer was in error, and an adjustment is being made in your account."
These are supposed to be the sheerest, blindest accidents. Mistakes are not believed to be the normal behavior of a good machine. If things go wrong, it must be a personal, human error, the result of fingering, tampering a button getting stuck, someone hitting the wrong key. The computer, at its normal best, is infallible.
I wonder whether this can be true. After all, the whole point of computers is that they represent an extension of the human brain, vastly improved upon but nonetheless human, superhuman maybe. A good computer can think clearly and quickly enough to beat you at chess, and some of them have even been programmed to write obscure verse. They can do anything we can do, and more besides.
It is not yet known whether a computer has its own consciousness, and it would be hard to find out about this. When you walk into one of those great halls now built for the huge machines, and standing listening, it is easy to imagine that the faint, distant noises are the sound of thinking, and the turning of the spools gives them the look of wild creatures rolling their eyes in the effort to concentrate, choking with information. But real thinking, and dreaming, are other matters. On the other hand, the evidence of something like an unconscious, equivalent to ours, are all around, in every mail. As extensions of the human brain, they have been constructed the same property of error, spontaneous, uncontrolled, and rich in possibilities.

The title of the writing "To Err is Human" implies that ______.

A. making mistakes is confined only to human beings
B. every human being cannot avoid making mistakes
C. all human beings are always making mistakes
D. every human being is born to make bad mistakes
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