4. Раскрыть скобки: a) 4(5y + 2x)(5y – 2x) б) (3x3 - 2y2)3

a) $$4(5y+2x)(5y-2x) = 4((5y)^2 - (2x)^2) = 4(25y^2 - 4x^2) = 100y^2 - 16x^2$$ б) $$(3x^3 - 2y^2)^3 = (3x^3)^3 - 3(3x^3)^2(2y^2) + 3(3x^3)(2y^2)^2 - (2y^2)^3 = 27x^9 - 54x^6y^2 + 36x^3y^4 - 8y^6$$