题目

．若函数f(x)＝的定义域为R，则a的取值范围是________． 答案：解析 ∵f(x)的定义域为R，所以2x2＋2ax－a－1≥0恒成立， 即x2＋2ax－a≥0恒成立， ∴Δ＝4a2＋4a≤0，－1≤a≤0. 答案 [－1,0]完形填空      We are all busy talking about using the Internet,but how many of us know the history of the Internet?      Many people are 1 when they find that the Internet was set up in the 1960s. At that time,computers 2 large and expensive. Computer networks didn't work well. If one computer in the network 3 down,the whole network stopped. 4 a new network system (系统) had to be set up. It should be 5 to be used by many different computers. If part of the network was not working, 6 could be sent through another part. In this way computer network system would keep on 7all the time.      At first the Internet was only used by the government,but in the early 1970s,universities,hospitals and banks were allowed to use it too. However,computers were still very expensive and the Internet was difficult to use. By the start of the 1990s? computers became cheaper and 8 to use. Scientists had also developed software that made “surfing”(浏览) the Internet more convenient.      Today it is easy to get online and it is said that millions of people use the Internet every day. 9 e-mail is more and more popular among students. The Internet has now become one of 10 parts of people's life.() 1. A. surprise   B. surprising   C. surprised   D. surprises() 2. A. is   B. are   C. was   D. were() 3. A. break   B. breaks   C. broke   D. would break() 4. A. Because   B. So   C. But   D. However() 5. A. good enough   B. well enough   C. enough good   D. enough well() 6. A. information   B. informations   C. an information   D. the informations() 7. A. work   B. to work   C. working   D. worked() 8. A. easy   B. easily   C. more easily   D. easier() 9. A. Send   B. Sending   C. To be sent   D. Sent() 10. A. important   B. more important            C. most important   D. the most important