This is a practical example of Vygotsky's "zone of proximal development" theory, which holds that there are two levels of students' development: one is the existing level of students, which refers to the level of problem-solving that can be achieved when they are independent; The other is the possible development level of students, that is, the potential gained through teaching. The difference between them is the nearest development zone. Teaching should focus on students' recent development zone, provide students with more difficult content, arouse students' enthusiasm, give full play to their potential, surpass their own recent development zone, reach their own level of difficult development, and then carry out the development of the next development zone on this basis.