题目

Listen to the passage and fill in the missing words.Since the film Jaws was played in 1975, people have always been of sharks. Many people who the film started to believe that sharks were bad animals that ate humans. Some people started fishing for sharks, as many as they could. At that time, nobody cared if sharks were killed or how many sharks were killed. People just wanted them killed.After1975, large sharks fell quickly around the world. This was not only fear of sharks, but also finning. Finning would have an effect upon Peter Benchley, the man who wrote the book the film Jaws base已知1x-1y=1x+y，试求yx-xy的值．