\( \displaystyle x^3+6x^2+12x = 1323 \)
\( \displaystyle x^3+\underbrace{6}_{a}x^2+\underbrace{12}_{b}x\quad \underbrace{- 1323}_{c}=0 \)
\( \displaystyle \underbrace{\left(x+\frac{a\vphantom{a^2}}{3}\right)^{3}}_{z^3} + \underbrace{\left(b-\frac{a^2}{3}\right)}_{p} \cdot \underbrace{\left(x+\frac{a\vphantom{a^2}}{3}\right)}_{z} + \underbrace{\left(\frac{2 a^{3}}{27}-\frac{a b}{3}+c\right)}_{q} = 0 \)
\(\displaystyle z=\sqrt[3]{-\frac{q}{2}+\sqrt{\left(\frac{q}{2}\right)^{2}+\left(\frac{p}{3}\right)^{3}}}+\sqrt[3]{-\frac{q}{2}-\sqrt{\left(\frac{q}{2}\right)^{2}+\left(\frac{p}{3}\right)^{3}}} \)
\( \displaystyle x=z-\frac{a}{3} = 9\)
