The monotonicity of the function函数的单调性也叫函数的增减性。函数的单调性是对某个区间而言的，它是一个局部概念。The monotonicity of the monotonicity of the function is also called function. The monotonicity of the function on an interval is concerned, it is a local concept.定义Definition一般地，设函数f(x）的定义域为I：In general, a function f (x) domain of I:如果对于属于I内某个区间上的任意两个自变量的值x1、x2，当x1x2时都有f(x1)f(x2).那么就说f(x）在这个区间上是增函数(另一种说法为单调不减函数)。如果f(x1)f(x2)，那么就说f(x）在这个区间上是严格增函数（另一种说法是增函数）。If for any belongs to some interval I on the two
