The full name of Li Er's letter of criticism is: Peking University Yanyuan Li Zhengyuan Li Yongle's letter of criticism. Because two professors, Li, are both from the Department of Mathematics of Peking University, among them, Li is famous for studying the postgraduate entrance examination of linear algebra.

In fact, everyone is similar to the real question, and Li Yongle or Chen Wendeng can do it.

I recommend some review materials for postgraduate mathematics:

Li Yongle 660 questions

Li Yongle Linear Algebra Lecture Video

The order of use of these reference books is to lay a solid foundation by reviewing the whole book, then fill in the blanks with 660 multiple-choice exercises, and finally simulate the real questions.

The key to reviewing mathematics lies in solid operation, linear algebra lies in clever calculation based on understanding, and probability lies in clear memory of relevant knowledge and definitions. I wish you a smooth postgraduate entrance examination.