a2-b2=(a-b)(a+b)
(2-x)*(2+x)=-
2
(a-2)*(a+2)=2-
(2-cd)*(2+cd)=-(
)2
(8b-2)*(8b+2)=*
2-
(8b-2)*(8b+2)=(*
)2-
(4-m)*(4+m)=-
2
(z-4)*(z+4)=2-
(4-cd)*(cd+4)=-(
)2
(2b-4)*(2b+4)=*
2-
(2b-4)*(4+2b)=(*
)2-
(8ab-zx)*(zx+8ab)=*(
)2-(
)2
(8z+a)*(a-8z)=2-
*
2
(mlu+8k)*(8k-mlu)=*
2-(
)2
(4bc3-8x)*(8x+4bc3)=*b2c6-
*
2
(4bc3-8x)*(8x+4bc3)=(*bc3)2-
*
2