T459

f(x) = 1 / (x^(2) + 1)
f' = Derivative(f)
f''(x) = f''(x)
A = Intersect(f'', xAxis, (-0.5773502691896241, 0))
B = Intersect(f'', xAxis, (0.5773502695631735, 0))
P: (x(A), f'(x(A)))
S: (x(A), f(x(A)))
g = Tangent(S, f)