a)
[tex]2xy + xy + x = 3xy + x[/tex]
b)
[tex]3mn + ( - 3mn) + 3= 3[/tex]
c)
[tex]2 {x}^{2} - 2x + ( - 2 {x}^{2} ) + 4x = 2x[/tex]
d)
[tex] {a}^{2} - {b}^{2} + 2 {b}^{2} - 2{a}^{2} = {b}^{2} - {a}^{2} [/tex]
e)
[tex] - pq - q + ( - pq) + q = - 2pq[/tex]
f)
[tex] {x}^{2} - 2 {y}^{2} + ( - {x}^{2} ) + 2 {y}^{2} + 2xy = 2xy[/tex]
