中文摘要：

通过无界函数与函数趋于无穷大的关系和中值定理只在实数范围内成立两个反例,说明运用反例思想有利于加深学生对概念、定理的理解,培养学生思维的严密性,从而提高教学效果.

英文摘要：

By two counter-examples of the relationship between unbounded function and conclusion that the function goes to infinity and the fact that the mean value theorem only works in the range of real number, it is stated that counter-examples idea can make students understand conceptions and theorems better, and foster the preciseness of students＇ thinking, so the teaching effect can be increased.