问题
解答题
已知一直线与椭圆4x2+9y2=36相交于A、B两点，弦AB的中点坐标为M（1，1），求直线AB的方程．
答案
解：设通过点M（1，1）的直线方程为y=k（x﹣1）+1，
代入椭圆方程，整理得（9k2+4）x2+18k（1﹣k）x+9（1﹣k）2﹣36=0
设A、B的横坐标分别为x1、x2，则
解之得
故AB方程为
4x+9y﹣13=0．
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已知一直线与椭圆4x2+9y2=36相交于A、B两点，弦AB的中点坐标为M（1，1），求直线AB的方程．
解：设通过点M（1，1）的直线方程为y=k（x﹣1）+1，
代入椭圆方程，整理得（9k2+4）x2+18k（1﹣k）x+9（1﹣k）2﹣36=0
设A、B的横坐标分别为x1、x2，则
解之得
故AB方程为4x+9y﹣13=0．
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| Look at this photo. The boy in a blue jacket is my good friend. 1 name is David. He’s fourteen years old. He likes playing 2 very much and he has a great sports collection. He has ten 3 , twenty basketballs and thirty baseballs. He also 4 sports on TV. His brother John 5 sports, too. But he has a small sports 6 . He has five basketballs, six baseballs 7 only one soccer ball. They 8 a good computer, but they 9 like computer games. They always say it is 10 and it’s not good for their study. They are really sports fans but not computer fans. Don’t you think so?
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