题目

已知点A(1，2)和B(－2，5)，试求出两个二次函数，使它们的图象都经过A、B两点． 答案：解 法一 设抛物线y＝ax2＋bx＋c经过点A(1，2)，B(－2，5)， 则①－②得3b－3a＝－3，即a＝b＋1. 设a＝2，则b＝1，将a＝2，b＝1代入①，得c＝－1， 故所求的二次函数为y＝2x2＋x－1. 又设a＝1，则b＝0，将a＝1，b＝0代入①，得c＝1， 故所求的另一个二次函数为y＝x2＋1. 法二 因为不在同一条直线上的三点确定一条阅读理解。          It was an exciting moment for Shen Xue and Zhao Hongbo, a retired married couple from Harbin, China. It was also a great moment for China because it was the country's first gold medal in the pairs figure (花样) skating competition at the 2010 Vancouver Winter Olympic Games.      Everyone was very quiet when Shen and Zhao were skating onto the ice. They were expecting something wonderful to happen. As soon as the music started, Shen and Zhao skated around the field quickly withbeautiful style; every move was perfect. When the music stopped, all the people cheered. In the end Shen and Zhao won the Olympic gold medal.      In China, winter sports are not as popular as they are in America and Northern European countries. SoChina sent only 90 athletes to Vancouver to take in a few, carefully chosen sports. Such a good decision alsoled to Wang Meng and Zhao Yang winning gold medals in the little known, but exciting sports of short track (轨道) speed skating.      China did not win a lot of medals at these Winter Games. Most of the events are still very new to China and need to be developed. But Chinese athletes learn very quickly. For example, China's women's curling team (冰壶队) only began in 2003, but they were No. 1 at the 2009 World Women's Curling Championship.      This means that with hard work and a bit of luck, China's winter stars could soon shine on the world stage. 1. Shen Xue won the gold medal in the ________ event at the 2010 Vancouver Olympics. A. pairs of figure skating B. short track speed skatingC. women's curlingD. long track speed skating 2. The people were ________ when Shen Xue and Zhao Hongbo started skating at the games. A. noisy B. quiet C. cheeringD. excited 3. The underlined (画线) word "couple" means ________ in Chinese. A. 对手B. 朋友C. 夫妻 D. 同事 4. China's women's curling team won't be eight years old until ________. A. 2003 B. 2009 C. 2010 D. 2011 5. What made China's winter athletes get such a success? A. Luck. B. A chance.C. Hard work and a little luck. D. The country's support.