Monotonicity of the monotone decreasing plus monotone decreasing function is decreasing.

Monotonicity of the monotone increasing decreasing function is increasing.

The monotonically decreasing monotonically increasing function is decreasing.

Multiplication and division are uncertain.

monotonic function

Generally assume a continuous function? If the domain of f(x) is d, then

If the values of any two independent variables belonging to an interval in the domain d are x 1, x2∈D and x1>; X2, both with f(x 1) > f(x2), that is, it is monotonous and monotonically increasing in D, so F(x) is increasing function in this interval.

On the other hand, if the values of any two independent variables belonging to an interval in the domain D are both x 1, x2∈D and X 1 >: X2, both of them are equal to f (x 1).