Ответ:

  1. а) \(\frac{13x^{-9}}{y^{-6}}\cdot\frac{y}{52x^{-5}}=\frac{13}{52}x^{-9-(-5)}y^{6+1}=\frac14x^{-4}y^7=\frac{y^7}{4x^4}\).
  2. б) \(\frac{21a^{-4}}{10b^6}\cdot\frac{5b^{-6}}{7a^{-6}}=\frac{21\cdot5}{10\cdot7}a^{-4-(-6)}b^{-6-6}=\frac32a^2b^{-12}=\frac{3a^2}{2b^{12}}\).