ĐKXĐ:...
(2y−xx−y−x2−xy−2y2x2+y2+y−2):x2+y+xy+x4x4+4x2y+y2−4
=[2y−xx−y−(x+y)(x−2y)x2+y2+y−2]:(x+1)(x+y)(2x2+y)2−4
=(x+y)(x−2y)−(x−y)(x+y)−(x2+y2+y−2):(x+y)(x+1)(2x2+y−2)(2x2+y+2)
=(x+y)(x−2y)−2x2+2−y.(2x2+y−2)(2x2+y+2)(x+y)(x+1)
=(2y−2)(2x2+y+2)x+1