a2-b2=(a-b)(a+b)
(1-x)*(1+x)=-2
(a-1)*(a+1)=2-
(1-cd)*(1+cd)=-()2
(2b-1)*(2b+1)=*2-
(2b-1)*(2b+1)=(*)2-
(10-m)*(10+m)=-2
(z-10)*(z+10)=2-
(10-cd)*(cd+10)=-()2
(1b-10)*(1b+10)=*2-
(1b-10)*(10+1b)=(*)2-
(2ab-zx)*(zx+2ab)=*()2-()2
(2z+a)*(a-2z)=2-*2
(mlu+2k)*(2k-mlu)=*2-()2
(10bc3-2x)*(2x+10bc3)=*b2c6-*2
(10bc3-2x)*(2x+10bc3)=(*bc3)2-*2