a = -2.3000000000000003
f_a(x) = x^(3) + a x^(2)
E: (-2 a / 3, 4 a^(3) / 27)
W: (-a / 3, 2 a^(3) / 27)
f_2(x) = x^(3) + 2 x^(2)
f_1(x) = x^(3) + x^(2)
f_0(x) = x^(3)
f_{-0,5}(x) = x^(3) - 0.5 x^(2)
f_{-1}(x) = x^(3) - x^(2)
f_{-2}(x) = x^(3) - 2 x^(2)