This book will be more painful to brush if it doesn't have enough foundation. In the preface, Mr. Pei Liwen has explained the topics of students who are suitable for the postgraduate entrance examination in mathematics (that is, non-mathematics majors). Among them, the topics with five-pointed stars should be studied emphatically, and the topics with asterisks are not enough knowledge of advanced mathematics, so you need to learn a few points to have a certain understanding.