Ответ:

  1. \(5a(5a^2-8a+4)=25a^3-40a^2+20a\).
  2. \(7b^3(7b^3-2b^2+1)=49b^6-14b^5+7b^3\).
  3. \((-5c^2+0.3c)(-2.5c^3)=12.5c^5-0.75c^4\).
  4. \(0.2d(2.2d^3-0.5d^2+3.1)=0.44d^4-0.1d^3+0.62d\).

Ответ: 1) \(25a^3-40a^2+20a\); 2) \(49b^6-14b^5+7b^3\); 3) \(12.5c^5-0.75c^4\); 4) \(0.44d^4-0.1d^3+0.62d\).