(x的平方+2xy+y的平方）的平方+16
=[(x+y)^2]^2+16
=(x+y)^4+16��ʽ�ֽ� ���dz˻���ʽ- -Ӧ����(x��ƽ��+2xy+y��ƽ������ƽ��-16=[(x+y)^2]^2-16=(x+y)^4-16=[(x+y)^2+4][(x+y)^2-4]=[(x+y)^2+4](x+y+2)(x+y-2)