函数值域是中学数学的重点内容,也是历年高考常考的知识点。理解、掌握函数值域的概念,灵活、熟练求较简单函数的值域,掌握求函数值域的基本策略,从实质入手,而不是从表面的、杜燥的方法入手,是教学中必须达到的教学目的。我们知道,函数是一种特殊的映射:设A,B是非空的数集,如果按某个确定的对应关系f,使对于集合A中的任意一个数 Function domain is the focus of secondary mathematics, but also the historical examination of the college entrance examination knowledge points. Understand and grasp the concept of function range, flexible, skilled to compare the range of simple functions, to grasp the basic strategy of seeking value range, starting from the substance, rather than from the surface, Du dry method is the teaching must be achieved The purpose of teaching. We know that the function is a special mapping: Let A, B is a non-empty number set, according to a certain correspondence f, so that for any number in the set A