求变量的范围是解析几何中的常见题型,也是高考的热点,同时也是学生学习中的难点.解决这类问题的基本方法是先寻找所求变量与其它变量的关系,建立相应的函数、方程或不等式,将问题转化为求函数、方程或不等式中有关变量的取值范围;然后应用函数、方程或不等式方法求出所求变量的取值范围.这类问题综合性强,需通过对实例的剖析、讨论,才能逐步掌握它的处理方法.下面试图通过 Finding the range of variables is a common question type in analytic geometry, and it is also a hot spot of the college entrance examination. It is also a difficult point in student learning. The basic method to solve such problems is to first find the relationship between the desired variable and other variables, and establish the corresponding function, The equation or inequality transforms the problem into a range of values ​​for the relevant variables in a function, equation, or inequality; it then applies a function, equation, or inequality method to find the range of values ​​for the desired variable. This type of problem is comprehensive and requires The analysis and discussion of examples can gradually grasp its processing methods. The following attempts have been made