Basic formulas must be memorized. Those derived from formulas are not necessary in theory, but it is also a waste of time to derive them when using them, so you can't escape from the backrest formula. Have compassion. hahaha. I think there is only one skill, and that is to do more exercises. Don't trust the experts who solve a plenary session. Although the problems are ever-changing, although there are laws to be found, the changes are always diverse. Only by deeply understanding the formula theorem and some experience in doing problems can we pass the exam, and these two abilities are accumulated bit by bit in doing problems at ordinary times. Those with high talent can do fewer problems, and those with low talent can still occupy high school mathematics if they are skilled in doing more problems. Hehe, I hope it helps you.