392. 1) (1-0,3a+0,15a²)·4a; 2) (2,25x²-1,5xy+2,5y²)·(-2,4xy); 3) 1⅓ab·(¾a²b-⅚ab²-b³)

Решение:

• 1) \( (1-0.3a+0.15a^2) \cdot 4a = 4a - 1.2a^2 + 0.6a^3 \)
• 2) \( (2.25x^2 - 1.5xy + 2.5y^2) \cdot (-2.4xy) = -5.4x^3y + 3.6x^2y^2 - 6xy^3 \)
• 3) \( \frac{4}{3}ab \cdot (\frac{3}{4}a^2b - \frac{5}{6}ab^2 - b^3) = \frac{4}{3}ab \cdot \frac{3}{4}a^2b - \frac{4}{3}ab \cdot \frac{5}{6}ab^2 - \frac{4}{3}ab \cdot b^3 \)
  \( = a^3b^2 - \frac{10}{9}a^2b^3 - \frac{4}{3}ab^4 \)