[m]\frac{a^{4/3} - 8a^{1/3}b}{a^{2/3} + 2\sqrt[3]{ab} + 4b^{2/3}}\cdot(1-2\cdot \sqrt[3]{\frac{b}{a}})^{-1}= \frac{a^{1/3}\cdot(a - 8b)}{a^{2/3} + 2a^{1/3}b^{1/3} + 4b^{2/3}}\cdot(1-\frac{2b^{1/3}}{a^{1/3}})^{-1}=[/m]
[m]=\frac{a^{1/3}\cdot(a^{1/3} - 2b^{1/3})(a^{2/3} + 2a^{1/3}b^{1/3} + 4b^{2/3})}{a^{2/3} + 2a^{1/3}b^{1/3} + 4b^{2/3}}\cdot (\frac{a^{1/3}-2b^{1/3}}{a^{1/3}})^{-1}=[/m]
[m] = a^{1/3}\cdot(a^{1/3} - 2b^{1/3}) \cdot \frac{a^{1/3}}{a^{1/3}-2b^{1/3}}=a^{1/3}\cdot a^{1/3} = a^{2/3}[/m]