That's what math is like. Many people want to finish the exam quickly and then leave time to check. In fact, it is difficult for people to detect their own mistakes, because there are thinking patterns, just like it is difficult to see typos in their own compositions. The best way is to develop good habits when doing problems at ordinary times. Don't be careless with every question, and do it carefully. Only in this way can we reduce the chances of making mistakes in the exam. Of course, it is hard to avoid it completely. After all, full marks are not so easy to get. You can only introduce yourself as much as possible to avoid making mistakes.

The most fundamental way to solve big problems is to lay a good foundation. No matter how complicated the big question is, it is also composed of basics, because it is impossible to give a question that you can only answer through the knowledge you have not learned. So after laying a good foundation, see the big problem, analyze it carefully, analyze what the problem is, and where you may need to start. The key to analysis is to practice more at ordinary times and then summarize. What may be tested in such a question, what to do, what to do in such a question, and what to test. There are many types of topics, so I'm not afraid to read them.

In short, learning is not a one-off event, and it takes a period of hard work.

If you have a good foundation, it should be an easy process for you. But you must have such awareness, and then you can do it. Otherwise, no matter how simple things are, they will not succeed if they are not done.