Lage der Hochpunkte

k = 2.7 (slider from -5 to 5, step 0.1)
f(x) = (1 / 3 * x^(3)) - (k * x)
g: y = If[x < 0, ((-(2 / 3)) * x^(3))]
H, B = Extremum(f(x))
a = false