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