Question

преобразуйте (3х-у)(9х^2+6xy+y^2)

Answer 1

$(3x-y)(9x^2+6xy+y^2)=(3x-y)(3x+y)^2 = \\ = (3x-y)(3x+y)(3x+y) = ((3x)^2-y^2)(3x+y) = \\ = (9x^2-y^2)(3x+y) = 27x^3+9x^2y-3xy^2-y^3$