4. Раскрыть скобки: а) 3(5y + 2x)(5y - 2x) = 3[(5y)^2 - (2x)^2] = 3(25y^2 - 4x^2) = 75y^2 - 12x^2 б) (x^2 - y^3)^2 = x^4 - 2x^2y^3 + y^6

а) 3(5y + 2x)(5y - 2x) = 3(5y)^2 - 3(2x)^2 = 3(25y^2 - 4x^2) = 75y^2 - 12x^2

б) (x^2 - y^3)^2 = (x^2 - y^3)(x^2 - y^3) = x^2(x^2) - x^2(y^3) - y^3(x^2) + y^3(y^3) = x^4 - 2x^2y^3 + y^6