Thanks for sending the link.
The first graph (the cubic) is x3 - 9x (roots of 3, -3 and 0); therefore, the derivative is 3x2 - 9 and evaluated at x=0 is -9. The graph doesn't make it look that steep, but it is.
The second graph is apparently a quartic with a double root at 0, i.e. x4 - 9x2 which obviously has derivative 0 at x=0.