Mathematics is an exam that constantly solves problems, and the types of questions are limited. So you have to do a lot of problems to find the feeling of solving problems. Without enough questions, you can't sum up useful classification, even if you take my notes and read them directly, it's meaningless. Because this is not a Chinese exam. But if you just brush the questions, you may get a high score when the exam is simple, such as 15. Once the examination becomes more difficult, the examination room will be overwhelmed and at a loss. For example, I have a research friend who passed 15 in Tsinghua Mathematics in World War I, but was not admitted to a specialized course. World War II mathematics is still just a brush, and the third year of World War II mathematics dropped from 16 to 120. The change of difficulty has a great influence on grades. Therefore, only by summarizing the types of questions and knowledge points can we have a clear mind when facing difficult problems and find a hidden breakthrough in solving problems.