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问题 解答题

已知二次函数f（x）的二次项系数为a，且不等式f（x）＞﹣4x的解集为（1，3），若f（x）的最大值大于﹣3，求a的取值范围

答案

解：设f（x）=ax2+bx+c，（a＜0），

由题意得方程f（x）=﹣4x两个根是1，3，

即ax2+（b+4）x+c=0两个根是1，3．

∴

∴b=﹣4a﹣4，c=3a

又f（x）的最大值大于﹣3，

即

消去b，c得到关于a不等式，a2+5a+4＞0

解得a的取值范围是﹣1＜a＜0或a＜﹣4．

单项选择题

Are you a man or a mouse When people ask this question they want to know (1) you think you are a (2) person or a coward. But you will never really know the answer to this question (3) you are tested in real life. Some people (4) they are brave but when they come face to face with real (5) , they act like cowards. Others think of themselves as cowards, but when they meet danger, they act like (6) .Lenny had always thought of himself as a (7) person. He got worried before examinations. He worried about his job and health. All he wanted in life was to be safe and healthy. (8) , on January 15th, 2002, a plane crashed into the Potomac River in Washington. Lenny went to the river to See what was happening. He saw a woman in the (9) water. Lenny did not feel afraid. He kept very (10) and did a very dangerous thing. He jumped into the Potomac, (11) to the woman, and kept her head (12) the water. Seventy-eight people died that day. Thanks to Lenny, it was not (13) .When you are in a very (14) situation and feel afraid, the body automatically produces a chemical in the blood. The chemical is called adrenalin. (15) adrenalin in the blood system, you actually feel per and per and are (16) to fight or run away. However, when you are absolutely terrified, the body can produce too much adrenalin. Where this (17) , the muscles become very hard and you find you (18) move at all. You are then paralyzed with fear. This is (19) when we are very frightened, we sometimes say we’re "petrified". This word comes from the Greek word "petros", which means "stone". We are (20) frightened that we become stonelike.

第（8）空应选择（）

A．So

B．Therefore

C．Then

D．Actually
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名词解释

子宫峡
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