任务型阅读

   ①The meaning of shaking the head is not always the same in different countries. Maybe some visitors would be surprised when they first came to India. When talking to an Indian, he would often shake his head. The visitors might think that the Indian did not like what they said. But, in fact, they would be completely(完全地)wrong.

   Indians always shake their heads when they talk to each other. It does not have the same meaning as“No”. If someone wants  ②  (visit)India, he should know this, or it will give him some trouble.

   One day, a foreign officer went to  ③  on business. He leased(租用)a car and hired(雇用)an Indian to drive it. When he told his driver to send him to his office, the Indian shook his head at once. The officer said again, and the driver shook his head again. At last, the officer, of course, got angry.

   “Why do you refuse(拒绝)my order(要求)? ”he shouted. “Drive me to my office at once! ”

   The driver answered in a quite loud voice, too. “Yes, sir! ”But to the officer’s surprise, the driver shook his head at the same time.

The car started, and the foreign officer was now too surprised to say a word. He thought about it for a while, and then ④he nodded with a smile, “‘No’ means ‘Yes’ here! ”

—No, the ruler is ________

先化简，再求值：（$\frac{x}{x+y}$﹣$\frac{x^2}{x^2+2xy+y^2}$）÷（$\frac{x}{x+y}$﹣$\frac{x^2}{x^2-y^2}$），其中x=$\sqrt{2}$，y=1．