[tex]\bf a^{\frac{{ n}}{{ m}}} \implies \sqrt[{ m}]{a^{ n}} \qquad \qquad
\sqrt[{ m}]{a^{ n}}\implies a^{\frac{{ n}}{{ m}}}\\\\
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\left( x^{\frac{2}{9}} \right)^{\frac{3}{8}}\implies x^{\frac{2}{9}\cdot \frac{3}{8}}\implies x^{\frac{6}{72}}\implies x^{\frac{1}{12}}\implies \sqrt[12]{x}[/tex]