a)
[tex]4x \times (3x - 2y + 5) - ( - 2y) \times ( - 2x + y - 4) = 12 {x}^{2} - 8xy + 20x + 2y( - 2x + y - 4) = 12 {x}^{2} - 8xy + 20x - 4xy + 2 {y}^{2} - 8y = 12 {x}^{2} + 2 {y}^{2} - 12xy + 20x - 8y[/tex]
b)
[tex]4x \times ( - 2x + y - 4) + 3x - 2y + 5 = - 8 {x}^{2} + 4xy - 16x + 3x - 2y + 5 = - 8 {x}^{2} + 4xy - 13x - 2y + 5[/tex]
