When you do the calculation, throw the answer aside and stimulate your adrenaline. Think that when you encounter this kind of calculation problem in the exam, do it yourself. No one answered. Do it for a while, and then check the answers and fill in the scores yourself; Play the habit of calculation, such as preparing draft paper, and have confidence in the answers you have calculated. This kind of thing is like remembering the taste of food, and the feeling of "remembering" is not afraid in the future.