函数的存在性和任意性问题,是一种常见题型,也是高考的热点之一.它们既有区别又有联系,意义和转化方法各不相同,容易混淆.对于这类问题,利用函数的相关知识,可以把相等关系转化为函数值域之间的关系,不等关系转化为 Existence and arbitrariness of the function, is a common type of question, but also one of the hot spots in the college entrance examination. They both the distinction and the connection, the meaning and the transformation method are different, easy to confuse .For such problems, the use of function Relevant knowledge, the equivalent relationship can be transformed into the function of the relationship between the value range, ranging from the relationship into