Ответ:

  1. \(\dfrac{14a}{b^{-3}}\cdot\dfrac{b^{-2}}{56a^4}=\dfrac{14ab^3b^{-2}}{56a^4}=\dfrac{1}{4}a^{-3}b=\mathbf{\dfrac{b}{4a^3}}\).
  2. \(\dfrac{18x^{-6}}{y^5}\cdot\dfrac{7y^{-5}}{6x^{-12}}=\dfrac{18\cdot7}{6}x^{-6-(-12)}y^{-5-5}=21x^6y^{-10}=\mathbf{\dfrac{21x^6}{y^{10}}}\).