for special product, use the formula: [tex] (x+y)^{3} [/tex] = [tex] x^{3} + 3 x^{2} y+3x y^{2} + y^{3} [/tex]
so, [tex] (2x-4y)^{3} [/tex] = [tex] (2x)^{3} + 3 (2x)^{2} (-4y) +3(2x) (-4y)^{2} + (-4y)^{3} [/tex]
=[tex] 8x^{3} -48x^{2} y+96x y^{2} -64y^{3} [/tex]
