Writing a power function, because the knowledge points contained in the inverse proportional function are fragmentary, can better grasp the time of the open class, in addition, it is beneficial for students to ask questions and strengthen the interaction between teachers and students, thus adding luster to the open class. Secondly, the difficulty of the course can also be determined according to the students' situation. From the basic knowledge to the integration with other functions, it is more difficult and conducive to control.