有理数的加减混合运算是初一代数的重要内容之一．“九义”大纲明确规定：“熟练掌握有理数的运算法则，灵活运用运算律简化计算．”认真分析题目的结构特点，灵活使用一些技巧，则可方便运算，使解题更简捷．其技巧可概括为五“结合”：一、互为相反数的一对有理数首先结合； The addition and subtraction of a rational number is one of the important contents of the first generation number. The “Nine Righteousness” outline clearly stipulates: “Proficient in the arithmetic of rational numbers, and flexible use of operational laws to simplify calculations.” Carefully analyzing the structural characteristics of topics and flexibly using some techniques can facilitate operations and make problem solving more simple. The techniques can be summarized as five “combinations”: First, a pair of rational numbers that are mutually opposite numbers are combined firstly;