[tex]a) - 2xy(x + 3y) + 4x(xy - {y}^{2} )[/tex]
[tex] = - 2 {x}^{2} y - 6x {y}^{2} + 4 {x}^{2} y - 4x {y}^{2} [/tex]
[tex] = 2 {x}^{2} y - 10x {y}^{2} [/tex]
[tex] = 2xy(x - 5y)[/tex]
[tex]b)5x(x - 3) - 4x(2x - 3) + 3x(x + 1)[/tex]
[tex] = 5 {x}^{2} - 15x - 8 {x}^{2} + 12x + 3 {x}^{2} + 3x[/tex]
[tex] = 0[/tex]
[tex]d)(x + 4)(x - 3) - (x - 1)(x + 6)[/tex]
[tex] = {x}^{2} - 3x + 4x - 12 - {x}^{2} - 6x + x + 6[/tex]
[tex] = -4x - 6[/tex]
[tex] = 2(-2x - 3)[/tex]
