Aus Online Mathematik Brückenkurs 2
The function has zero derivative at three points, x=a, x=b and x=c (see picture below), which are therefore the critical points of the function.
The point x=b is an inflexion point because the derivative is positive in a neighbourhood both to the left and right.
At the left endpoint of the interval of definition and at x=c, the function has local maximum points , because the function takes lower values at all points in the vicinity of these points. At the point x=a and the right endpoint, the function has local minimum points.
Also, we see that x=c is a global maximum (the function takes its largest value there) and the right endpoint is a global minimum.
Between the left endpoint and x=a, as well as between x=c
and the right endpoint, the function is strictly decreasing (the larger x is, the smaller f(x) becomes), whilst the function is strictly increasing between x=a and x=c (the graph flattens out at x=b, but it isn't constant there).