According to today's headline data, the function is difficult to learn because there are many changes, and the same formula may have many different changes or combinations. Understanding problems, lack of practice, incorrect practice methods, and failure to master relevant skills and methods. Can not adapt to the change of function, not good at grasping the invariance of change.

Function is the most essential part of the whole junior middle school, and it is the mathematical logic from "number" to "algebraic expression" to "function". Junior high school began to learn rational numbers, and the range of rational numbers framed the corresponding range of junior high school mathematics. From the counting formula, we further enrich our understanding of logarithm, and complete the transformation from natural number to algebraic expression and fraction to number, which is a changing number.