First, double the linear function, quadratic function, inverse proportional function and trigonometric function to see what a function is; In my understanding, I tell my students that if one quantity changes, the other quantity will also change, just like your parents are moving and you are moving. Then the first variable is called the independent variable, and the subsequent changes are called the dependent variable. In junior high school, the independent variable is represented by X, and the dependent variable is represented by Y ... There is no Y in the derivative. Writing y as f(x) shows that this is a function with x as the independent variable, and all functions can draw his image. The derivative is the slope of the tangent of each point on these images. If you can't understand the actual meaning, there is a derived formula, which can be used directly after memorizing it. Don't be afraid!