题目

       For many years scientists have said that the earth is getting warmer. Now they have found something new-hot cities! In the southern US, they have found that cities become very hot in summer. For example, the city of Atlanta in Georgia has roof(屋顶) temperature of up to 50oC while it is 27℃ in the streets! At night, the outside of buildings stays so hot that the heat of the city causes storms over the city!        China also has the same kind of problems. Every year more farmland is used for factories or offices. More housing is needed, too. As people become rich方程（x-1）x=x-1的根为x=1x=1．