10.4 √[4]{a}:√[8]{a⁻⁵}.

$$ \frac{\sqrt[4]{a}}{\sqrt[8]{a^{-5}}} = \frac{a^{\frac{1}{4}}}{a^{-\frac{5}{8}}} = a^{\frac{1}{4} - (-\frac{5}{8})} = a^{\frac{1}{4} + \frac{5}{8}} = a^{\frac{2}{8} + \frac{5}{8}} = a^{\frac{7}{8}} $$

Ответ: a^(7/8)