9.4 5√a⁴ ⋅ 10√a⁷.

$$\sqrt[5]{a^4} \cdot \sqrt[10]{a^7} = a^{\frac{4}{5}} \cdot a^{\frac{7}{10}} = a^{\frac{4}{5} + \frac{7}{10}} = a^{\frac{8 + 7}{10}} = a^{\frac{15}{10}} = a^{\frac{3}{2}}$$

Ответ: $$a^{\frac{3}{2}}$$.