You can also watch the Olympic Games. There are many methods and ideas that can be used in class, such as the fixed point method of series and the generating function method. These are classic methods, which are much simpler than the undetermined coefficients taught by the teacher in class.

I think mental arithmetic is very important, hehe, I practiced but didn't insist ... I suggest you analyze geometry with your mouth and find a big topic. My experience is that only two topics are counted in one class. In fact, my speed is mainly forced by my classmates. I remember sitting with him and finding that he was super fast (unimaginable at that time), which greatly affected my self-confidence. So I compare with him every day, and gradually I am almost the same as him. In fact, I am the same in junior high school. The deskmate next to me is not fast, but she is super accurate. I also compare with him. As a result, I soon had this ability.

Besides, I can't be proud. Finish the last joint exam half an hour in advance and step up the inspection. The result is still 138. At first glance, the simplest of the multiple-choice questions and fill-in-the-blank questions is wrong! Really want to cry without tears!