The difference between mathematics 30 years ago and now: mathematics 30 years ago is closely related, easy to learn and easy to remember. There are so many expanded contents that it is difficult for students to master and find the key points. The previous textbooks are concise and straightforward, with both scientific knowledge and moral education connotation. You can teach yourself, or you can use examples or reference books to complete the task by yourself. At present, the content of the textbook is cumbersome and rambling, and the problem that can be clearly explained in one sentence seems to be confusing you on purpose.