It is necessary to do math exercises. Under normal circumstances, only 60% to 70% of the learning knowledge can be clearly explained in class, and the rest should be clarified, consolidated and improved in practice. You can do it selectively when you do the problem. Proportion: If you master some knowledge well, you can do less or even nothing. We should decide according to our own actual situation. Judging from your introduction, you are not very good at math, and you are not particularly diligent. I mean to explain the basic knowledge clearly and learn it firmly before doing the optimization problem. If you can't finish your usual homework carefully, it only shows that you are irresponsible to yourself. If you have a good grasp of the basic questions, then it is very appropriate for you to do the optimization questions. When you solve a difficult problem, you will feel as happy as winning a battle!