a = 1.2 (slider from -5 to 5)
b = 1.6 (slider from -5 to 5)
c = 2.9 (slider from -5 to 5)
f(x) = (a * x^(2)) + (b * x) + c
A = If(a > 0, Min[f, -10, 10], Max[f, -10, 10])
B: (0, c)
g = Tangent(B, f)
B2 = NaN
t1, h, i, j = Polygon(B, (0 + 1, c), Intersect[g(x), x = 1])