Ответ:

  1. \(0.96x^6-1.38x^4\).
  2. \(0.3a^6b-1.2a^5b^2+a^4b\).
  3. \(0.5a^3b^3-a^2b^2+0.9ab\).
  4. \(0.3a^3b^6+0.4a^2b^6-a b^5\).
  5. \(12x^{n+1}y-8x^ny^{n+1}\).