a2-b2=(a-b)(a+b)
(5-x)*(5+x)=-
2
(a-5)*(a+5)=2-
(5-cd)*(5+cd)=-(
)2
(3b-5)*(3b+5)=*
2-
(3b-5)*(3b+5)=(*
)2-
(9-m)*(9+m)=-
2
(z-9)*(z+9)=2-
(9-cd)*(cd+9)=-(
)2
(5b-9)*(5b+9)=*
2-
(5b-9)*(9+5b)=(*
)2-
(3ab-zx)*(zx+3ab)=*(
)2-(
)2
(3z+a)*(a-3z)=2-
*
2
(mlu+3k)*(3k-mlu)=*
2-(
)2
(9bc3-3x)*(3x+9bc3)=*b2c6-
*
2
(9bc3-3x)*(3x+9bc3)=(*bc3)2-
*
2