1, the popular meaning of a function is the relationship determined by independent variables and dependent variables. There may be one, two or n independent variables, but when the independent variables are determined, the variable values are also unique.

2. The meaning of function is that in the field of mathematics, function is a relationship, which makes each element in one set correspond to the only element in another set.

Characteristics of functions

1, Boundedness

Let the function f(x) be defined on the interval x, if there is m >；; 0, for all X belonging to the interval X, there is always |f(x)|≤M, then f(x) is bounded on the interval X, otherwise F (x) is unbounded on the interval.

2. Monotonicity

Let the domain of the function f(x) be D, and the interval I is contained in D. If for any two points x 1 and x2 on the interval, when X 1

Then the function f(x) is called monotonically increasing in the interval i; If for any two points x 1 and x2 on the interval I, when X 1