题目

阅读理解 Many students feel it difficult to remember new words when they begin to study English. Now I will give you some advice. 1. Do not waste（浪费） time in learning a list(词汇) of English words. It is the hardest way to remember English words. How do you learn to speak Chinese? You did it by listening carefully to the people talking to each other. You can find radio programs, TV programs and records, and listen to them carefully. The best way to learn all new words is through ear. As you listen to more and more dialogues, you will learn how English is pronounced in p已知抛物线y=kx2-2kx+9-k（k为常数，k≠0），且当x＞0时，y＞1．（1）求抛物线的顶点坐标；（2）求k的取值范围；（3）过动点P（0，n）作直线l⊥y轴，点O为坐标原点．①当直线l与抛物线只有一个公共点时，求n关于k的函数关系式；②当直线l与抛物线相交于A、B两点时，是否存在实数n，使得不论k在其取值范围内取任意值时，△AOB的面积为定值？如果存在，求出n的值；如果不存在，说明理由．