a2-b2=(a-b)(a+b)
(6-x)*(6+x)=-
2
(a-6)*(a+6)=2-
(6-cd)*(6+cd)=-(
)2
(1b-6)*(1b+6)=*
2-
(1b-6)*(1b+6)=(*
)2-
(8-m)*(8+m)=-
2
(z-8)*(z+8)=2-
(8-cd)*(cd+8)=-(
)2
(6b-8)*(6b+8)=*
2-
(6b-8)*(8+6b)=(*
)2-
(1ab-zx)*(zx+1ab)=*(
)2-(
)2
(1z+a)*(a-1z)=2-
*
2
(mlu+1k)*(1k-mlu)=*
2-(
)2
(8bc3-1x)*(1x+8bc3)=*b2c6-
*
2
(8bc3-1x)*(1x+8bc3)=(*bc3)2-
*
2