题目

用所给词的适当形式填空。 learn, have, write, start, call 1. I ________ to ride a bike when I was four years old. 2. Students usually ________ learning English in primary schools. 3. They ________ a big party to celebrate （庆祝） the harvest last October. 4. Professor Li stopped ______ after he had a heart disease. 5. I ________ Lucy last night, but she was not at home. 答案：1. learned   2. start   3. had   4. writing   5. called（2012•安徽模拟）过抛物线y=x2上异于原点的任意两点A、B所作的两条切线交于点P，且交x轴于M、N（如图），F为抛物线的焦点．（Ⅰ） 求点P的坐标（用A、B的横坐标x1和x2表示）；（Ⅱ）求证：|FP|2=|FA|•|FB|；（Ⅲ）设S△OAB=λS△PMN，试求λ的值．