代数式的求值,是中学教学中的重要内容,是学好数学的一项重要基本功,其应用十分广泛,技巧性很强.在各种类型的考试中,特别是在数学竞赛中,代数式的求值是常见的命题题型.下面根据题的类型举例说明代数式求值的方法.1　因式分解法例1　已知a +b+c=0 ,求a 1b +1c +b 1c +1a +c 1a Algebraic evaluation is an important part of middle school teaching. It is an important basic skill for learning mathematics. It is widely used and very skillful. In various types of exams, especially in mathematics competitions, algebraic expressions are required. Values ​​are common propositional questions. The following example illustrates algebraic expressions based on the type of question. 1 Factorization in the known case of a +b+c=0, find a 1b +1c +b 1c +1a +c 1a