a2-b2=(a-b)(a+b)
(3-x)*(3+x)=-
2
(a-3)*(a+3)=2-
(3-cd)*(3+cd)=-(
)2
(6b-3)*(6b+3)=*
2-
(6b-3)*(6b+3)=(*
)2-
(13-m)*(13+m)=-
2
(z-13)*(z+13)=2-
(13-cd)*(cd+13)=-(
)2
(3b-13)*(3b+13)=*
2-
(3b-13)*(13+3b)=(*
)2-
(6ab-zx)*(zx+6ab)=*(
)2-(
)2
(6z+a)*(a-6z)=2-
*
2
(mlu+6k)*(6k-mlu)=*
2-(
)2
(13bc3-6x)*(6x+13bc3)=*b2c6-
*
2
(13bc3-6x)*(6x+13bc3)=(*bc3)2-
*
2