We all know Ebbinghaus forgetting curve, people's memory will be forgotten with the passage of time, so it is normal that both the learned mathematical formula and the learned China poems will be forgotten. We can memorize it again and again. When we send it for the first time, within a week, we can memorize it again and again, reaching a state of memorization. It is best to understand mathematical formulas. Instead of just remembering some simple tuned letters, you will remember them better. It is also important to use them. You can put the formula in the question and use it together. Constant use can also achieve the state of memory.