数学竞赛中一些涉及代数式(或方程)的求值问题,若囿于常规思路方法求解,往往会颇费周折,甚至笨拙不堪;但如能把握题设特征,注意到所要考察的代数式的取值情况,进行灵活、合理的估算,确定其范围,常能使问题渐趋明朗,达到柳暗花明的境地.现举例说明如下,供参考. Some mathematics contests involving the evaluation of algebraic equations (or equations) will often be awkward and even clumsy if they are not solved by conventional methods of thinking. However, if you can grasp the characteristics of the questions, note the algebraic values ​​to be investigated. The situation, the flexible and reasonable estimation, the determination of its scope, can often make the problem become clearer, to achieve a bright and clear situation. Here are examples for reference, for reference.