It must be remembered that formulas include conditions.

3 Listen carefully.

You should use your head when doing exercises. First of all, you should think about what the problem is, what kind of mathematical knowledge is involved, and what formula should be used. Then you should think about whether the teacher has talked about similar exercises before completing the problem. After you finish, you should also think about whether there is an easier way. What knowledge does this topic tell you? The purpose of doing the problem is to master the question type, understand the knowledge and improve the ability. If you do this every time, then,