我们知道,充要条件可以和高中数学的任何一部分知识结合,能有效地考查学生灵活运用数学知识和数学思想的能力,因此是历年高考命题的热点.一般来讲,在涉及字母参数范围的充要条件问题中,常常利用集合的包含关系来考虑问题.解决此类问题首先要弄清以下几个基本事实.(证略)已知集合A={x|x满足条件p},B={x|x满足条件q}. We know that the necessary and sufficient conditions can be combined with any part of the knowledge of high school mathematics, and can effectively examine the students’ ability of using mathematics knowledge and mathematics thoughts effectively. So it is the hot topic of college entrance examination proposition in the past years.In general, To solve these problems, we must first understand the following basic facts: A = {x | x satisfies the condition p}, B = { x | x satisfies the condition q}.