Đáp án:
\(B=\sqrt[3]9\)
Giải thích các bước giải:
\(\begin{array}{l}
\quad B = \dfrac{2}{\sqrt[3]3 - 1}- \dfrac{4}{\sqrt[3]9 - \sqrt[3]3 + 1}\\
\to B = \dfrac{2\left(\sqrt[3]9 + \sqrt[3]3 + 1\right)}{\left(\sqrt[3]3 - 1\right)\left(\sqrt[3]9 + \sqrt[3]3 + 1\right)}- \dfrac{4\left(\sqrt[3]3 + 1\right)}{\left(\sqrt[3]3 + 1\right)\left(\sqrt[3]9 - \sqrt[3]3 + 1\right)}\\
\to B = \dfrac{2\left(\sqrt[3]9 + \sqrt[3]3 + 1\right)}{3-1} - \dfrac{4\left(\sqrt[3]3 + 1\right)}{3+1}\\
\to B = \sqrt[3]9 + \sqrt[3]3 + 1 - \left(\sqrt[3]3 + 1\right)\\
\to B = \sqrt[3]9
\end{array}\)
