We have
(2x^2 - 3y)^3 =
C(3,0)(2x^3)^3 * (3y)^0 - C(3,1) (2x^3)^2(3y)^1 + C(3,2)(2x^3)^1 (3y)^2 + C(3,3)(2x^3)^0 (3y)^3 =
1 (8x^9) - 3 (4x^6)(3y) + 3 (2x^3)(9y^2) + 1 ( 27y^3)
The coefficients are in red
And the final expansion is
8x^9 - 36x^6y + 54x^3y^2 - 27y^3
