谁知道a^3+12a^2=126这个方程怎么解?

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谁知道a^3+12a^2=126这个方程怎么解?
谁知道a^3+12a^2=126这个方程怎么解?

谁知道a^3+12a^2=126这个方程怎么解?
盛金公式:

x³ + 12x² - 126 = 0
a = 1,b = 12,c = 0,d = -126
A = b² - 3ac = 144
B = bc - 9ad = 1134
C = c² - 3bd = 4536
∆ = B² - 4AC < 0


第四个公式:
T = 1/64
θ = arccosT ≈ 1.5552
θ/3 ≈ 0.5184
x₁ ≈ -10.9489
x₂ ≈ -3.9583

x₃ ≈ 2.9073

{{a = -4 + 16/(-1 + 3 I Sqrt[455])^(1/3) + (-1 + 3 I Sqrt[455])^(
1/3)}, {a = -4 - (8 (1 + I Sqrt[3]))/(-1 + 3 I Sqrt[455])^(1/3) -
1/2 (1 - I Sqrt[3]) (-1 + 3 I Sqrt[455])^(1/3)}, {a = -4 - (
8 (1 - I Sqrt[3]))/(-1 + 3 I Sqrt[455])^(1/3) -
1/2 (1 + I Sqrt[3]) (-1 + 3 I Sqrt[455])^(1/3)}}