. Firstly, the absolute value is obtained by partition method: that is, let x>a and x < = a. In two cases, the range of a is calculated separately, and finally the union is obtained. Methods: The maximum and minimum values of f(x) were solved. Solve the maximum and minimum values of g(x). The minimum value of g(x) is greater than f(x), and the maximum value of g(x) is less than f(x). By using the implicit condition that g(x) is a monotone function on the domain, the range of A is narrowed. ? The way to solve the problem is the most important.

Comment on the second floor first? The college entrance examination questions are also well thought out.