f(x)=ax²+bx+c

a = 1 (slider from -5 to 5, step 0.1)
b = 2 (slider from -5 to 5, step 0.01)
c = -1 (slider from -10 to 10, step 0.1)
f(x) = a * x^(2) + b * x + c
text4: "f(x)=" + (LaTeX[f]) + ""
A = Extremum(f)