Solving cubic equation of one variable Finally, there is a process x^3+3x^2-3x-9=0

Solving cubic equation of one variable Finally, there is a process x^3+3x^2-3x-9=0

x^3+3x^2-3x-9=0
x²(x+3)-3(x+3)=0
(x+3)(x²-3)=0
X = - 3 or x = ± root 3