Function is a necessary mathematical knowledge to enter junior high school. The learning of functions started from the last semester of Grade Two (according to People's Education Edition), and the learning contents include linear functions (including positive and negative proportional functions), quadratic functions and simple trigonometric functions. After entering senior three, I began to learn the exponential function, logarithmic function and power function of senior three, and the trigonometric function deepened. The first function begins in the last semester of the eighth grade, the inverse proportional function begins in the next semester of the eighth grade, and the quadratic function and trigonometric function begin in the ninth semester.

Function is a general model for creating formulas describing quantitative information relations, which provides a patterned method for creating general formulas and makes it easier and more convenient. In our life, functions may not be used a lot, and the functions that will be used are the simplest functions, such as buying things, how much money can buy a few pounds, or how much money can buy several bags of things; How far can a car go in a few minutes? These are actually functional relationships, and functions are everywhere in life. Therefore, it is very important to learn functions, and everyone should learn function knowledge well.