a)
[tex]4x( {x}^{2} - 3x) - ( {x}^{3} - 2x + 5) = 4 {x}^{3} - 12 {x}^{2} - {x}^{3} + 2x - 5 = 3 {x}^{3} - 12 {x}^{2} + 2x - 5[/tex]
b)
[tex]3 {y}^{2} (x - y) + 2x( {y}^{2} - x + 3y) = 3x {y}^{2} - 3 {y}^{3} + 2x {y}^{2} - 2 {x}^{2} + 6xy = 5x {y}^{2} - 2 {x}^{2} - 3 {y}^{3} + 6xy[/tex]
c)
[tex]2x(x + y) - 4( {x}^{2} - xy + y) = 2 {x}^{2} + 2xy - 4 {x}^{2} + 4xy - 4y = - 2 {x}^{2} + 6xy - 4y[/tex]
d)
[tex]5xy(2x + 3y) - 3x(xy - 2 {y}^{2} ) = 10 {x}^{2} y + 15x {y}^{2} - 3 {x}^{2} y + 6x {y}^{2} = 7 {x}^{2} y + 21x {y}^{2} [/tex]
