a2-b2=(a-b)(a+b)
(1-x)*(1+x)=-2
(a-1)*(a+1)=2-
(1-cd)*(1+cd)=-()2
(4b-1)*(4b+1)=*2-
(4b-1)*(4b+1)=(*)2-
(12-m)*(12+m)=-2
(z-12)*(z+12)=2-
(12-cd)*(cd+12)=-()2
(1b-12)*(1b+12)=*2-
(1b-12)*(12+1b)=(*)2-
(4ab-zx)*(zx+4ab)=*()2-()2
(4z+a)*(a-4z)=2-*2
(mlu+4k)*(4k-mlu)=*2-()2
(12bc3-4x)*(4x+12bc3)=*b2c6-*2
(12bc3-4x)*(4x+12bc3)=(*bc3)2-*2