All right. This kind of teaching aid is relatively difficult, and it can also be suitable for students with above average grades. The content of the test questions in the supplementary materials tends to expand training and has strong analogy. If you don't have a certain mathematical foundation, the questions inside will be difficult to do. Many of the questions in this teaching aid are real questions of famous schools. When solving problems, we must pay attention to the problem-solving methods and think carefully, and we will certainly get good results.