定义域与值域相同的函数具有良好的保值性,经常出现在全国各地的模拟考试试题和高考试题中.应用这类函数可以设计许多综合试题,例如求参数的取值范围问题、讨论方程根的个数问题以及函数与数列的综合问题等.加强这方面的训练,可以让学生感受数学的美,提高他们学习数学的兴趣;可以提高学生运用函数和方程的思想、数形结合的思想分析问题、解决问题的能力.1求参数的取值范围 The same domain and value domain function has good hedging, often appear in the simulation test questions and college entrance examination questions all over the country.Using such functions can be designed many comprehensive questions, such as seeking the range of parameters, discuss the root of the equation The number of questions and the function and sequence of comprehensive issues, etc. Strengthening training in this area, allowing students to experience the beauty of mathematics to improve their interest in learning mathematics; can improve the students to use the functions and equations of thought, combined with the number of ideological analysis Problems, the ability to solve the problem .1 seeking the range of parameters