1, the content is comprehensive and systematic: The Complete Book of Quan Yi, a special training course for ninth grade mathematics, gives a comprehensive and systematic introduction to all the knowledge points of ninth grade mathematics, covering all the contents of ninth grade mathematics, and provides detailed problem-solving methods and exercises to help students fully understand and master mathematics knowledge.

2. Selected topics and examples: Quan Yi's "Training Book for Ninth Grade Mathematics Special Class" provides a large number of selected topics and examples, with moderate difficulty. Examining the application and understanding ability of each knowledge point is helpful for students to consolidate their knowledge and cultivate their problem-solving skills and thinking ability.