初中阶段 ,我们共经历了两次数系的扩展 .在初一 ,引入负数 ,将我们对数的认识扩展到有理数的范围 ;在初二 ,学习了无理数 ,将数的范围进一步扩展到实数 .我们主要从以下几方面学习实数 .　　 一、实数的概念　　对实数 ,教材是这样介绍的 :有理数和无理数统称为实数 .因此要学 In the junior high school stage, we experienced a total expansion of two times. In the first day, we introduced negative numbers to extend our understanding of logarithms to the scope of rational numbers. In the second day, we learned irrational numbers and further extended the range of numbers to real numbers. Mainly from the following aspects to learn real numbers. First, the concept of real numbers for real numbers, teaching materials are introduced as follows: rational numbers and irrational numbers are collectively referred to as real numbers. Therefore we must learn