The answers can be found in course forums, question-and-answer platforms, textbooks and reference books.

1, course forum: Many online education platforms have course forums where you can communicate with other students and find answers.

2. Q&A platform: For example, Zhihu and Baidu know that many professionals and schoolmasters are willing to share their knowledge and experience on these platforms.

3. Textbooks and reference books: You can consult relevant textbooks or reference books to find answers or ideas to solve problems.