题目

若二次函数y=ax2+bx+c的x与y的部分对应值如下表：则下列说法错误的是（ ）x…-10123…y…… A. 二次函数图像与x轴交点有两个B. x≥2时y随x的增大而增大C. 二次函数图像与x轴交点横坐标一个在－1~0之间，另一个在2~3之间D. 对称轴为直线x=1.5 答案：【答案】D【解析】根据x=1时的函数值最小判断出抛物线的开口方向; 根据函数的对称性可知当x=2时的函数值与x=0时的函数值相同, 并求出对称轴直线方程可得答案.A、由图表数据可知x=1时, y的值最小, 所以抛物线开口向上. 所以该抛物线与x轴有两个交点.故本选项正确;B、根据图表知, 当x≥2时y随x的增大而Proverbs (谚语) are quite common in spoken English. We don’t normally put them in a composition or a letter. Sometimes it is helpful if you know what common proverbs mean. Here are a few examples.1) “Once bitten, twice shy.” If a dog bites me, I shall be twice as careful in future when I see it. This proverb is also used to apply to many things and not only to dogs. If you have been cheated at a shop, you will not go the same shop again.2) “A bird in the hand is worth two in the bush.” If I am a hunter, trying to catch birds, it is better to catch one than to see two birds in a bush but not able to catch them. Thus this means that what you have already got is better than the chance of being able to get something bigger in future.3) “Too many cooks spoil the broth (soup)”. When too many people do something, they get in each other’s way and do a bad job.4) “To pour oil on troubled waters” is to try to calm things down. Oil is lighter than water. If a ship is in trouble at sea, another ship may come to help it. The second ship can send small boats to rescue people. However, it may first pour oil on the sea to make the sea less rough.5) “Don’t be a dog in a manger(槽)”means“ Don’t be selfish.” In a stable (马房), the manger is the place where the horse’s food is put. Sometimes a dog will sleep in the manger and bark when a horse comes to get its food. The dog does not want to eat the lay in the manger but it will not let the horse eat it.6) “He is sitting on the fence” means that somebody will not say whether he is in favor of a plan or against it. He is sitting on a fence between two opposing sides, perhaps waiting to see which side will win.7) “He who pays the piper calls the tune.” A piper is a musician. The man who employs or pays a musician can say what tunes the man will play. Thus this means that if a man provides the money for a plan, he can say how it will be carried out.8) “You can’t get blood out of a stone” means that you cannot get something from a person who has not got any of the things you want. e. g. you cannot get a million dollars from a poor man. 1.Mr. and Mrs. Smith had a quarrel. Their friend, Mr. Brown, wanted to talk to them. When he came back, he told his wife that he had been trying to help the Smiths by ______.A. getting blood out of a stoneB. pouring oil on troubled watersC. sitting on the fenceD. being a dog in a manger2.Mr. Wang paid for a new school. Some people didn’t like the design of the school but they didn’t argue with Mr. Wang because ______.A. once bitten, twice shyB. he was sitting on the fenceC. a bird in the hand is worth two in the bushD. he who pays the piper calls the tune3.Mrs. Lin wanted to buy a new dress. Her husband suggested that she buy it from a shop near their home. Mrs. Lin disagreed because she had been cheated by that shop. So she said :“I won’t go there again because ______.”A. I am sitting on the fenceB. a bird in the hand is worth two in the bushC. too many cooks spoil the brothD. once bitten, twice shy4.Mr. Brown had quite a good job in Hong Kong but he thought that if he went to Singapore, he might get a much better job with more money and a larger house. His wife didn’t want him to leave his job in Hong Kong and she reminded him that ______.A. too many cooks spoil the brothB. a bird in the hand is worth two in the bushC. he who pays the piper calls the tuneD. you can not get blood out of a stone