题目

 “Our aim is to take our art to the world and make people understand what it is to move,” said David Belle, the founder of parkour(跑酷).  Close your eyes and imagine you are living in the next two centuries or more. You'll be living in a world filled with smart robots, which will be helping you to take care of your children, or your elderly parents in your home. You'll live much longer thanks to the medicine made by genetic (基因的) science. And mankind may be going farther in space than ever before-you will be living on the moon or Mars. How should we view the changes that反比例函数的图象与一次函数y=ax+b的图象交于A（1，3）和B（n,-1）两点.（1）求这两个函数的解析式，并画出草图;（2）根据图象回答当x取何值时，反比例函数的值大于一次函数的值;（3）连接OA、OB, 求⊿AOB的面积.