函数是初中数学的重点内容 ,同时又是难点 .由于变量的引进 ,使得这一部分内容抽象难懂 ,又因为这部分内容在初中代数中相对独立 ,因此 ,大部分同学感到难以掌握 .这部分内容所蕴涵的数形结合、函数建模、分类讨论等重要数学思想会对今后的学习和工作产生深刻影响 .为帮助大家 Function is the key content of junior high school mathematics, and it is also difficult. Because of the introduction of variables, this part of the content is abstract and difficult to understand, and because this part of the content is relatively independent in junior high school algebra, therefore, most of the students feel difficult to grasp. The important mathematics thoughts such as the combination of number and shape, function modeling, and classification discussion will have a profound impact on the future study and work. To help everyone