a2-b2=(a-b)(a+b)
(1-x)*(1+x)=-
2
(a-1)*(a+1)=2-
(1-cd)*(1+cd)=-(
)2
(3b-1)*(3b+1)=*
2-
(3b-1)*(3b+1)=(*
)2-
(2-m)*(2+m)=-
2
(z-2)*(z+2)=2-
(2-cd)*(cd+2)=-(
)2
(1b-2)*(1b+2)=*
2-
(1b-2)*(2+1b)=(*
)2-
(3ab-zx)*(zx+3ab)=*(
)2-(
)2
(3z+a)*(a-3z)=2-
*
2
(mlu+3k)*(3k-mlu)=*
2-(
)2
(2bc3-3x)*(3x+2bc3)=*b2c6-
*
2
(2bc3-3x)*(3x+2bc3)=(*bc3)2-
*
2