题目

已知⊙C经过点、两点，且圆心C在直线上.（1）求⊙C的方程；（2）若直线与⊙C总有公共点，求实数的取值范围. 答案：【答案】（1）（2）【解析】试题分析：(1)解法1：由题意利用待定系数法可得⊙C方程为.解法2：由题意结合几何关系确定圆心坐标和半径的长度可得⊙C的方程为.(2)解法1：利用圆心到直线的距离与圆的半径的关系得到关系k的不等式，求解不等式可得.解法2：联立直线与圆的方程，结合可得.试题解析：（阅读与回答问题 （本题共5小题；每小题2分，满分10分）Two Chinese farmers sang In Spring in their small room after drinking on a late August evening in Beijing. A friend put their song on the Internet. And soon they became stars around China.Wang Xu, 49, is from Henan, and Liu Gang, 34, is from Heilongjiang. They are among the millions of farmers who have gone to cities to work. "Although nobody pays attention to the music, I am singing happily, in streets, under bridges or in wild country, with no credit card, no girlfriend or a home with hot water, but only a guitar," they sing." It is just like the life we live now," Wang said." We are poor farmers, and you know people won't care about us." Their song is loved by millions of Chinese, including the people who are also from the countryside. Many people said they cried after listening to the song.Wang came to Beijing in 2000 and tried many jobs. Each month after he paid 600 yuan for the house and bought food, there was little money left. "I love music, and also want to make more money," Wang said. "I never dreamed of standing on such a big stage." Liu came to Beijing in 2003. "I wanted to try my luck in the big city," he said. And now their dreams of music have come true. They are really the luckiest of all the farmers in China.1.How old is Wang Xu ?______ 2. Where is Liu Gang from?______ 3.Why did Liu Gang come to Beijing in 2003?______ 4.Have their dreams of music come true?______ 5.What do you think of the two farmer singers?______