a = 6 (slider from 0 to 6, step 0.1)
f(x) = (-x^(3)) + (a * x^(2))
f0(x) = If[0 ≤ x ≤ a, f(x)]
gL: -0.5
amax: 6
f0k(x) = If[¬(0 ≤ x ≤ a), f(x)]
Text1: "f_{" + (LaTeX[a]) + "}"
gU: -5
gO: 50
gR: 6.5
Text2: "f_{\color{red}{" + (LaTeX[a]) + "}}(x) = -x^3 + {\color{red}{" + (LaTeX[a]) + "}}\;x^2"
A, H = Extremum(f)