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-
(7-m)*(7+m)=-
2
(z-7)*(z+7)=2-
(7-cd)*(cd+7)=-(
)2
(2b-7)*(2b+7)=*
2-
(2b-7)*(7+2b)=(*
)2-
(6ab-zx)*(zx+6ab)=*(
)2-(
)2
(6z+a)*(a-6z)=2-
*
2
(mlu+6k)*(6k-mlu)=*
2-(
)2
(7bc3-6x)*(6x+7bc3)=*b2c6-
*
2
(7bc3-6x)*(6x+7bc3)=(*bc3)2-
*
2