200平方厘米=____平方分米．

    Growing up is not always easy. When we face difficulties, we should never give up. We should try our best to make the life better. It is not useful to cry for help. Hong Zhanhui's story of growing from boy to man tells us about this.

    Hong was born in 1982 in a poor family in Henan Province. When he was only 11, his father became badly ill. And one day he came back with a baby girl. The girl was very young and they must spend much time looking after her. However, a year later, Hong's mother left home.____ So everything fell onto the young boy：to take care of his father and the sister, and to go on to study.

    Although his life was very hard, Hong didn't go away from his father and sister.____. He climbed tall trees to get birds' eggs for his sister. He walked two hours at weekends to the market to buy different things. Then he sold the things around his school to make some money.

    ____. To take care of his sister, he worked hard to rent（租） a room near his college for her, and sent her to school every day.

    When people knew Hong's story, he became a hero in people's eyes. Many people wanted to help him. But Hong refused the help from others. He said he felt happy by other's help, but he believed he could take care of his family by himself.____.

综合应用：如图3，⊙P与x轴相切于原点O，P点坐标为（0，6），A是⊙P上一点，连接OA，使tan∠POA=$\frac{3}{4}$，作PD⊥OA，垂足为D，延长PD交x轴于点B，连接AB．

①证明AB是⊙P的切点；

②是否存在到四点O，P，A，B距离都相等的点Q？若存在，求Q点坐标，并写出以Q为圆心，以OQ为半径的⊙O的方程；若不存在，说明理由