题目

已知函数，.（1）若在区间上单调递增，求m的取值范围；（2）求在区间上的最小值；（3）讨论在区间上的零点个数. 答案：【答案】（1）；（2）；（3）当时，函数有2个零点，当或时，函数有1个零点.【解析】（1）求出函数的对称轴，根据函数的单调性求出m的范围即可；（2）通过讨论m的范围，得到函数的单调区间，求出函数的最小值即可.（3）结合二次函数的实根分布即可求解（1）由题意，函数开口向上，对称轴的方程I entered St Thoma’s Hospital as a medical student at the age of 18 and spent five years there. I was an unsatisfactory student, for my heart, as you might have guessed, was not in it. I wanted, I had always wanted to be a writer, and in the evening, after my high tea, I wrote and read. Before long, I wrote a novel, called “Liza of Lambeth”, which I sent to a publisher and was accepted. It appeared during my last year at the hospital and had something of a success. It was of course an accident, but naturally I did not know that. I felt I could afford to give up medicine and make writing my profession; so, three days after I graduated from the school of medicine, I set out for Spain to write another book. Looking back now and knowing as I do the terrible difficulties of making a living by writing, I realize I was taking a fearful risk. It never even occurred to me. The next ten years were very hard, and I earned an average of £100 a year. Then I had a bit of luck. The manager of the Court Theatre put on a play that failed ; the next play he arranged to put on was not ready , and he was at his wits’ end. He read a play of mine and, though he did not much like it, he thought it might just run for the six weeks till the play he had in mind to follow it with could be produced. It ran for fifteen months. Within a short while I had four plays running in London at the same time. Nothing of the kind had ever happened before. I was the talk of the town. One of the students at St Thomas’s Hospital asked the famous surgeon with whom I had worked whether he remembered me. “Yes, I remember him quite well, “he said. “ One of our failures, I’m afraid. “ 1. Which of the following statements is not true? A. The author was very pleased to have his book published but he didn’t realize it was something of an accident. B. The success of his first book led the author to think he could afford to make writing his profession. C. The author knew he was running a terrible risk when he decided to become a writer. D. The author became a writer after graduation but was not a successful one. 2. In the second paragraph, “… he was at his wits’ end “means ________. A. he was having a nervous breakdown       B. he was out of his wisdom C. he did not know what to do            D. he almost went mad 3. The manager of the Court Theatre agreed to put the author’s play on the stage because _____________. A. he thought it would run for fifteen months B. he knew it was one of the author’s best plays shown in London C. he had just put on a play that failed D. the play he had arranged to put on was not ready 4. The author became the talk of the town. The reason was that __________. A. he talked with a great many people in London about his plays B. the plays he wrote were excellently performed in London C. his performances in the Court Theatre were unexpectedly D. he was criticized by an eminent surgeon as one of their failures