TeX Quellcode:
\underbrace{b}_{\sqrt[3]{b^3}}\cdot \sqrt[3]{\frac{1}{b}} = {\sqrt[3]{b^3} \cdot \sqrt[3]{\frac{1}{b}}= \sqrt[3]{\frac{b^3}{b}} = \sqrt[3]{b^2} = b^{2/3}