Increasing function and decreasing function
Generally speaking, let the domain of the function f(x) be I: if the values of any two independent variables belonging to an interval in I are x 1 and x2, then when X 1 < X2, there will be F (X 1) < F (X2). Then let's assume that f(x) is increasing function in this interval.
On the other hand, when X 1 < X2, if the values of any two independent variables belonging to an interval in I are F (x 1) > F (x2), then F (x) is a decreasing function in this interval.