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换元就是引入辅助未知数.把题中某一个(些)字母的表达式用另一个(些)字母的表达式来代换,这种解题方法,叫做换元法,又称变量代换法.换元法是初中数学非常重要的思想方法,在解分式方程时有着极为广泛的应用,能够达到化繁为简,化难为易,沟通已知和未知的联系,尤其是分式方程中,能够将分式方程转化为整式方程,使认知过程符合学生思维特点.换元要注意新旧变元的取值范围的变化.要避免代换的新变量的取值范围被缩小;若新变量的取值范
Replacement is the introduction of auxiliary unknowns. The problem of one (some) the expression of the alphabet with another (some) the expression of the letter to replace, this problem-solving method, called the yuan, also known as variable substitution The commutation method is a very important method of thinking in junior middle school mathematics. It has a very wide range of applications in the solution of fractional equations. It can achieve the purpose of simplifying, simplifying, and communicating the known and the unknown, especially in the fractional equation , Can convert the fractional equation into an integral equation, so that the cognitive process is consistent with the characteristics of the students thinking.Transformation yuan should pay attention to the change of the value range of the old and the new arguments.New variables to be avoided to replace the scope of the value is reduced; if the new The value of the variable range