a = 0.3 (slider from -5 to 5, step 0.1)
b = 1 (slider from -5 to 5, step 0.1)
c = -0.2 (slider from -5 to 5, step 0.1)
f(x) = a * x^(2.0) + b * x + c
Δ: b^(2.0) - 4.0 * a * c
text1: "Δ=" + Δ + ""