3) a) $$\frac{14a}{b^{-3}} - \frac{b^{-2}}{56a^{-4}}$$; 4) a) $$(\frac{5x^{-2}}{6y^{-1}})^3 \cdot 125x^6y^5$$

3.

1. a) \( \frac{14a}{b^{-3}} - \frac{b^{-2}}{56a^{-4}} = 14ab^3 - \frac{a^4}{56b^2} \)
2. 4) a) \( (\frac{5x^{-2}}{6y^{-1}})^3 \cdot 125x^6y^5 = (\frac{5^3 (x^{-2})^3}{6^3 (y^{-1})^3}) \cdot 125x^6y^5 = \frac{125 x^{-6}}{216 y^{-3}} \cdot 125x^6y^5 = \frac{125}{216} x^{-6} y^3 \cdot 125 x^6 y^5 = \frac{125 \cdot 125}{216} x^{-6+6} y^{3+5} = \frac{15625}{216} x^0 y^8 = \frac{15625}{216} y^8 \)