[tex] - 3 \times 2y \times (x \times 2 - y \times 2) - 2xy \times 2(x \times 2 - y \times 2) - ay \times (x \times 2 - y \times 2) \\ - 12 {x}^{2} y + 12x {y}^{2} 8 {x}^{2} y + 8x {y}^{2} - 2axy + 2a {y}^{2} \\ - 20 {x}^{2} y + 20x {y}^{2} - 2axy + 2a {y}^{2} [/tex]
