p = -1 (slider from -5 to 5, step 0.1)
f(x) = ((0.5 * (x^(2) + p)) * (x - p))
szöveg1: "f(x)=\frac{1}{2}(x^2+p)(x-p)=\\
=\frac{1}{2}(x^2+" + (LaTeX[p]) + ")(x-" + (LaTeX[p]) + ")"