\(x^3-x^2-x=\dfrac{1}{3}\Leftrightarrow3x^3-3x^2-3x-1=0\)
\(\Leftrightarrow4x^3-\left(x^3+3x^2+3x+1\right)=0\)
\(\Leftrightarrow4x^3-\left(x+1\right)^3=0\)
\(\Leftrightarrow\left(\sqrt[3]{4}.x\right)^3=\left(x+1\right)^3\)
\(\Leftrightarrow\sqrt[3]{4}.x=x+1\)
\(\Leftrightarrow x=\dfrac{1}{\sqrt[3]{4}-1}\)