代数式的求值在各省市每年的中考题或数学竞赛中都经常出现,一般方法是先化简,再代入,后计算．但有时若能从题目的结构特点出发,灵活应用,往往事半功倍．下面说说常用的方法和技巧．一、化简求值法这是求代数式值的最基本的方法,一般是化简复杂的部分．可以是化简已知条件,也可以化简代数式,对于复杂一些的两者都要化简． Algebraic evaluations often appear in the annual examination questions or math competitions in each province and city. The general method is to simplify, substitute and then calculate. However, if you can start from the structural characteristics of the topic, flexible application, often with less effort. Here to talk about commonly used methods and techniques. First, simplify the evaluation method This is the most basic method to find the algebraic type value, generally simplify complex part. Can simplify the known conditions, you can also simplify the algebraic formula, both for more complicated.