x_2 = -3 (slider from -5 to 5, step 0.5)
x_1 = 4 (slider from -5 to 5, step 0.5)
a = -1.45 (slider from -2 to 2, step 0.05)
f(x) = ((a * (x - x_1)) * (x - x_2))
texte1: "f(x)=" + f + ""