3) (-4m²n⁴/9p⁶k⁷)³.

3) $$\left(-\frac{4m^2n^4}{9p^6k^7}\right)^3 = -\frac{(4m^2n^4)^3}{(9p^6k^7)^3} = -\frac{4^3m^{2 \cdot 3}n^{4 \cdot 3}}{9^3p^{6 \cdot 3}k^{7 \cdot 3}} = -\frac{64m^6n^{12}}{729p^{18}k^{21}}$$

Ответ: -64m⁶n¹²/729p¹⁸k²¹