Respostas

2013-09-04T20:54:57-03:00
X^2 - y^2 -x - y 
(x+y)(x-y) -x -y
(x+y)(x-y-1)

Prova : 

(x+y)(x-y-1)
x^2-yx-x+yx-y^2-y . Cortando os yx e -yx
x^2-y^2-x-y