9. 5 √√0,000001 ⋅ √256.

9. $$5 \sqrt{\sqrt{0.000001} \cdot \sqrt{256}} = 5 \sqrt{\sqrt{10^{-6}} \cdot \sqrt{2^8}} = 5 \sqrt{10^{-3} \cdot 2^4} = 5 \sqrt{\frac{1}{1000} \cdot 16} = 5 \sqrt{\frac{16}{1000}} = 5 \sqrt{\frac{4}{250}} = 5 \frac{2}{\sqrt{250}} = \frac{10}{\sqrt{250}}$$.

Ответ: 10/$$\sqrt{250}$$