2(x2−y2)2\left(x^{2}-y^{2}\right)2(x2−y2)
2(y2−x2)2\left(y^{2}-x^{2}\right)2(y2−x2)
−2(x2+y2)-2\left(x^{2}+y^{2}\right)−2(x2+y2)
2(x2+y2)2\left(x^{2}+y^{2}\right)2(x2+y2)