根据问题的需要,用具体数值代替代数式中的字母,按照代数式中的运算关系计算,所得的结果是代数式的值.具体求解代数式的值的问题时方法很多,若选用方法恰当,很容易求出代数式的值,反之则运算量大又易出错.因此对于不同的题目,应根据其特征,采用简便、灵活的解题方法.下面结合例题谈谈代数式求值的 According to the needs of the problem, the concrete numerical value instead of the algebraic letters, according to algebraic computing relationship between the calculation, the result is algebraic value.Specific solutions to algebraic value of the problem in many ways, if the selection method is appropriate, it is easy to find Algebraic values, on the contrary, the operation is large and error-prone. So for different topics, should be based on its characteristics, the use of simple and flexible solution to the problem. The following combination of examples to talk about algebraic evaluation