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Last active May 12, 2020 02:10
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Cardano's Formula for a Cubic Equation
\[
x=\sqrt[3]{-\frac{b^3}{27a^3}+\frac{bc}{6a^2}-\frac{d}{2a}+\sqrt{\left(-\frac{b^3}{27a^3}+\frac{bc}{6a^2}-\frac{d}{2a}\right)^2+\left(\frac{c}{3a}-\frac{b^2}{9a^2}\right)^3}}+\sqrt[3]{-\frac{b^3}{27a^3}+\frac{bc}{6a^2}-\frac{d}{2a}-\sqrt{\left(-\frac{b^3}{27a^3}+\frac{bc}{6a^2}-\frac{d}{2a}\right)^2+\left(\frac{c}{3a}-\frac{b^2}{9a^2}\right)^3}}-\frac{b}{3a}
\]
\[
\newcommand{\p}{-\frac{b^3}{27a^3}+\frac{bc}{6a^2}-\frac{d}{2a}}
\newcommand{\q}{\sqrt{\left(\p\right)^2+\left(\frac{c}{3a}-\frac{b^2}{9a^2}\right)^3}}
x=\sqrt[3]{\p+\q}+\sqrt[3]{\p-\q}-\frac{b}{3a}
\]
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