2. Prepare well before class. Some people don't listen carefully in class because they don't understand. Actually, that's because you didn't attend class with questions. Listening without purpose will not have lasting attention. Preview the knowledge points before class and find out what you don't understand, so that you can learn according to your own situation in class.
3. Organize class notes. Don't think that mathematics is a subject where you don't have to take notes when you remember algorithms. In fact, math notes are indispensable. Some people are always stuck in one step when doing proof questions. That's because their proof method is too simple, essentially because their knowledge reserve is not solid.
4. Do a good review after class. Mathematics is a magical subject. When you understand a certain knowledge point, you master it. The digestion time in class is very short, so you need to spend some time reviewing in time after class to consolidate the knowledge points.