a2-b2=(a-b)(a+b)
(8-x)*(8+x)=-2
(a-8)*(a+8)=2-
(8-cd)*(8+cd)=-()2
(1b-8)*(1b+8)=*2-
(1b-8)*(1b+8)=(*)2-
(9-m)*(9+m)=-2
(z-9)*(z+9)=2-
(9-cd)*(cd+9)=-()2
(8b-9)*(8b+9)=*2-
(8b-9)*(9+8b)=(*)2-
(1ab-zx)*(zx+1ab)=*()2-()2
(1z+a)*(a-1z)=2-*2
(mlu+1k)*(1k-mlu)=*2-()2
(9bc3-1x)*(1x+9bc3)=*b2c6-*2
(9bc3-1x)*(1x+9bc3)=(*bc3)2-*2