有理数的概念是初一数学竞赛命题的热点之一,主要考查我们对有理数 概念的理解.现将这一部分的试题归类介绍如下: 一、考查正负数的性质 例1 a、b是有理数,如果|a-b|=a+b,那么对于结论:(1)a一定不是负数; The concept of rational numbers is one of the hot topics in the math contest. It mainly examines our understanding of the concept of rational numbers. Now we will classify the questions in this section as follows: First, examine the nature of positive and negative numbers. Examples 1 a and b are rational numbers. If |ab|=a+b, then for the conclusion: (1)a must not be negative;