10) (−1/3 a⁵y³)⁴ =

\(\left(-\frac{1}{3}a^5y^3\right)^4=\left(-\frac{1}{3}\right)^4a^{5\cdot4}y^{3\cdot4}=\frac{1}{81}a^{20}y^{12}\).

Ответ: \(\frac{1}{81}a^{20}y^{12}\)