a2-b2=(a-b)(a+b)
(2-x)*(2+x)=-
2
(a-2)*(a+2)=2-
(2-cd)*(2+cd)=-(
)2
(9b-2)*(9b+2)=*
2-
(9b-2)*(9b+2)=(*
)2-
(14-m)*(14+m)=-
2
(z-14)*(z+14)=2-
(14-cd)*(cd+14)=-(
)2
(2b-14)*(2b+14)=*
2-
(2b-14)*(14+2b)=(*
)2-
(9ab-zx)*(zx+9ab)=*(
)2-(
)2
(9z+a)*(a-9z)=2-
*
2
(mlu+9k)*(9k-mlu)=*
2-(
)2
(14bc3-9x)*(9x+14bc3)=*b2c6-
*
2
(14bc3-9x)*(9x+14bc3)=(*bc3)2-
*
2