If there is a solution once and for all, I still hope you can ask me. Some topics will be done if you see them, and some topics will not be done if you don't see them. Otherwise, there are so many problems you won't do. Sometimes I can see but I can't. This is the usual accumulation of experience. I may see the answer at a glance, but I just don't know how to explain it. Patchwork method, if you can't find a patchwork polynomial or single item, it is difficult to make it. I can introduce a method here for your reference.

When you encounter patchwork problems, don't think about spelling anything, because most of these problems appear in the proof questions, so you should start from the answers at this time and push back from the results of the proof. I have tried this method several times, and the effect is good, but some topics are difficult to push, which require your usual accumulation and can also be said to be inspiration.