y_S = 0.8 (slider from -5 to 5, step 0.1)
a = 0.4 (slider from -5 to 5, step 0.1)
x_S = 2 (slider from -5 to 5, step 0.1)
f_S(x) = a * (x - x_S)^(2.0) + y_S
p: -2.0 * a * x_S
q: a * x_S^(2.0) + y_S
f_N(x) = a * x^(2.0) + p * x + q
S: (x_S, y_S)