M6C Convex, concave, inflection
A function is convex (open upwards) in an interval when all its secant lines are above the graph of the function.
It is concave (open downwards) when the secant lines are below the graph.
Inflection point is the point where the function changes its curvature from convex to concave (or the other way round).
Move the point B, F and K around to see the convex and concave parts of the functions.