a2-b2=(a-b)(a+b)
(2-x)*(2+x)=-2
(a-2)*(a+2)=2-
(2-cd)*(2+cd)=-()2
(3b-2)*(3b+2)=*2-
(3b-2)*(3b+2)=(*)2-
(8-m)*(8+m)=-2
(z-8)*(z+8)=2-
(8-cd)*(cd+8)=-()2
(2b-8)*(2b+8)=*2-
(2b-8)*(8+2b)=(*)2-
(3ab-zx)*(zx+3ab)=*()2-()2
(3z+a)*(a-3z)=2-*2
(mlu+3k)*(3k-mlu)=*2-()2
(8bc3-3x)*(3x+8bc3)=*b2c6-*2
(8bc3-3x)*(3x+8bc3)=(*bc3)2-*2