2. Mapping must be learned, because mapping is the basis of functions, and only mapping can have functions. But the mapping in high school is shallow, and it is only explained when defining functions. When you go to college, you will learn more comprehensive surveying and mapping, and surveying and mapping will not be the focus of the college entrance examination.

Friendly reminder: as long as you listen to the class carefully, then do more questions and sum up by yourself (including the reasons for mistakes, expand your knowledge and draw small conclusions), you will definitely learn math well.