Junior high school began to learn functions, but those are basic functions, such as y=kx+b linear function, y=ax? +bx+c quadratic function, you must learn solid in junior high school, in fact, it is not difficult

Dependent variable (function): it changes with the change of independent variable. When the independent variable takes a unique value, the dependent variable (function) has and only has a unique value corresponding to it.

Function value: in a function where y is x, x determines a value, and y determines a value accordingly. When x takes a, y is determined as b, and b is called the function value of a. ..

Concept:

In the process of a change, the quantity that changes is called a variable (in mathematics, the variable is X, and Y changes with the change of the value of X), and some numerical values do not change with the variable, so we call them constants.

Independent variable (function): a variable related to other quantities, and any value in this quantity can find a corresponding fixed value in other quantities.

The corresponding rules of functions are usually expressed by analytical expressions, but a large number of functional relationships can not be expressed by analytical expressions, but only by images, tables and other forms.