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中考题中有关换元法的考题经常会见到,大部分要求用换元法解方程或方程组.有的是让考生写出换元后的方程(方程组)表达式;有的是让考生用换元法解方程或方程组.总之使用换元法时一定注意:①换元后使原方程或方程组变得简单明显.②能使解题步骤简单.③能使解题省时省力,过程简单,结果准确.④对求出的方程(方程组)的根一定要检验,避免出现增根或漏根现象.下面就用换元法解几类中考题,希望同学们掌握.解题时给出了详细分析,表示出怎样换元,换元后方程怎样表达,换元后方程怎样求根,最后怎样把原方程的根确定成一套完整的解题过程.
In the examination questions on the yuan for the law of the exam will often see, most of the requirements of the method used to solve equations or equations. Some are candidates for writing after the equation (equation) expression; some is for candidates to change method Solution of equations or equations.In short, the use of yuan for the law must pay attention to: ① for yuan after the original equations or equations become simple and clear. ② can solve simple steps. ③ can solve the problem of time-saving effort, the process is simple, The result is accurate.④For the root of the equation (system of equations) must be tested to avoid the phenomenon of increasing roots or leakage root. Here are several types of test questions by the redemption method, I hope the students to master. A detailed analysis shows how to change the yuan, after the yuan how to express the equation, after the yuan for roots how to find roots, and finally how to determine the root of the original equation into a complete solution to the problem.