Ответ: 8
\[\sqrt{\frac{16x^4}{y^6}} = \frac{\sqrt{16x^4}}{\sqrt{y^6}} = \frac{4x^2}{|y^3|}\]
\[\frac{4x^2}{|y^3|} = \frac{4 \cdot 4^2}{|2^3|} = \frac{4 \cdot 16}{8} = \frac{64}{8} = 8\]