40) \(-\frac{27}{1000}y^{15}x^9=\)

\(-\frac{27}{1000}=\left(-\frac{3}{10}\right)^3\), \(y^{15}=(y^5)^3\), \(x^9=(x^3)^3\).

\(-\frac{27}{1000}y^{15}x^9=\left(-\frac{3}{10}y^5x^3\right)^3\).

Ответ: \(\left(-\frac{3}{10}y^5x^3\right)^3\).