The most comprehensive answer should be a complete understanding of middle school textbooks.

The teacher asked me to buy reference books and big brands, such as Guide and Practice, Three-dimensional Design Optimization Scheme, Century Gold List and so on.

My opinion: it is best to buy a middle school textbook to fully understand your preview. Although there are not many questions, each question is quite classic. If I buy a textbook, the book really can't be complete.

If you are satisfied, adopt me. Thank you.