a = 1 (slider from -5 to 5, step 0.1)
b = -3 (slider from -5 to 5, step 0.1)
c = -1 (slider from -5 to 5, step 0.1)
d = 3.5 (slider from -5 to 5, step 0.1)
f(x) = (a * x^(3)) + (b * x^(2)) + (c * x^(1)) + d
Text1: "f(x) = " + f + ""
W = TurningPoint(f)