题目内容

设函数f(x)=-x(x-a)2(x∈R)，其中a∈R． (1)当a=1时，求曲线y=f(x)在点(2，f(2))处的切线方程； (2)当a≠0时，求函数f(x)的极大值和极小值，

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We unemployed share a social stigma (耻辱) similar to that of the rape victim. Whether consciously or subconsciously, much of the work-ethic driven public feels that you’ve somehow "asked for it". Secretly wanted to lose your job and "flirted (幻想)" with unemployment through your attitude- probably dressed in a way to invite it (left the vest unbuttoned on your three-piece suit). But the worse of it isn’t society’s work-ethic morality; it’s your own, which you never knew you had. You find out how much self-satisfaction was gained from even the most simple work-related task: a well-worded letter, a well-handled phone call, even a clean file. Being useful to yourself isn’t enough. But then almost everyone has heard about the need to be a useful member of society. What you didn’t know about was the loneliness. You’ve spent your life almost constantly surrounded by people, in classes, in dorms and at work. To suddenly find yourself with only your cat to talk to all day distorts (歪曲) your sense of reality. You begin to worry that fights of fancy might become one way. But you always were, and still are, stronger than that. You maintain balance and perspective, mainly through resorting frequently to sarcasm (嘲笑) and irreverence. Although something going wrong in any aspect of your life now seems to push you into temporary despair much more easily than before, you have some very important things to hang on to-- people who care, your sense of humor, your talents, your cat and your hopes. And beyond that, you’ve gained something- a little more knowledge and a lot more compassion. You’ve learned the value of the routine you scorned and the importance of the job you took for granted. But most of all, you’ve learned what a "7.6 percent unemployment rate" really means. What does "work-ethic" refer to

A. Crazy attitude toward work.
B. Public attitude toward work.
C. People who are working.
D. People who are out of work.

What are black holes This question is difficult to answer, since we do not have the necessary words to describe them. Scientists think that a black hole is a region of space into which matter has fallen and from which nothing can escape. So we cannot see a black hole. A black hole exerts a strong gravitational pull and yet it has no matter. It is only space. The exploration of black holes is just beginning. There are many speculations about them. There might be a huge hole at the centre of our galaxy swallowing up stars at a very rapid rate. Mankind may one day meet this fate. On the other hand, scientists have suggested that very advanced technology could one day harness the energy of black hole for human’s use on earth. These speculations sound like science fictions. But the theory of black holes is accepted by many scientists and astronomers.

Promptness is important in American business, academic, and social settings. The (56) of punctuality is taught to young children at school. Today slips and the use of bells signal to the child that (57) and time itself are to be respected. People who keep (58) are considered dependable. If people are late for job interviews, appointments, or classes, they are often (59) unreliable and irresponsible. In the business setting, "time is money" and companies may (60) their executive for tardiness to business meetings. Of course, it is not always possible to be punctual. Social and business etiquette also provides rules for (61) arrivals. Calling (62) the telephone if one is going to be more than a few minutes late for (63) appointments is (64) polite and is often expected. Keeping a friend waiting (65) ten to twenty minutes is considered rude. Respecting deadlines is also important in academic and professional (66) . Students who (67) assignments late may be surprised to find that the professor will (68) their grade or even refuse to (69) their work. (70) it is a question of arriving on time or of meeting a deadline, people are culturally expected to stick to the schedule time. Part Ⅳ ClozeDirections: In this part, there is a passage with 15 blanks. For each blank, there are 4 choices marked A, B, C and D. Choose the best answer for each blank and mark the corresponding letter with a single bar across the square brackets on your machine-scoring ANSWER SHEET.

A. on
B. in
C. at
D. to

圆心在原点上与直线x+y-2=0相切的圆的方程为______．