a2-b2=(a-b)(a+b)
(8-x)*(8+x)=-
2
(a-8)*(a+8)=2-
(8-cd)*(8+cd)=-(
)2
(7b-8)*(7b+8)=*
2-
(7b-8)*(7b+8)=(*
)2-
(2-m)*(2+m)=-
2
(z-2)*(z+2)=2-
(2-cd)*(cd+2)=-(
)2
(8b-2)*(8b+2)=*
2-
(8b-2)*(2+8b)=(*
)2-
(7ab-zx)*(zx+7ab)=*(
)2-(
)2
(7z+a)*(a-7z)=2-
*
2
(mlu+7k)*(7k-mlu)=*
2-(
)2
(2bc3-7x)*(7x+2bc3)=*b2c6-
*
2
(2bc3-7x)*(7x+2bc3)=(*bc3)2-
*
2