题目

Last year Tom left school. He came to Beijing to  41   a job. He went from one company to another but  42   wanted him. Now he had little money. He had to go back his small town. So he came to the station. He felt  43   and tired. It was very late at night and the  44    was full of people. They were waiting  45   tickets of the last train. He bought the last ticket, and he was very happy. At that time, a woman with a crying baby walked to him. She asked him to sell her the ticket. He gave her the ticket. He thought they needed it  46   he did. After the train left, 如图，抛物线关于轴对称，它的顶点在坐标原点，点P(1,2),,均在抛物线上.（1）求该抛物线方程；（2）若AB的中点坐标为，求直线AB方程.