Given a number set A, assuming that the element in it is X, now apply the corresponding rule F to the element X in A, and record it as f(x), and get another number set B. Assuming that the element in B is Y, the equivalent relationship between Y and X can be expressed as y=f(x).
The concept of function includes three elements: definition field A, value field C and corresponding rule F, among which the core is corresponding rule F, which is the essential feature of function relationship.
Extended data:
It changes with the change of the independent variable. When the independent variable takes a unique value, the dependent variable (function) has and only has a unique value corresponding to it.
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. ..
Functions are related to inequalities and equations (elementary functions). Let the function value be equal to zero. From a geometric point of view, the value of the corresponding independent variable is the abscissa of the intersection of the image and the X axis.
From the algebraic point of view, the corresponding independent variable is the solution of the equation. In addition, replacing "=" in the expression of a function (except a function without expression) with "",and then replacing "y" with other algebraic expressions, the function becomes an inequality, and the value range of the independent variable can be found.
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