a2-b2=(a-b)(a+b)
(8-x)*(8+x)=-2
(a-8)*(a+8)=2-
(8-cd)*(8+cd)=-()2
(2b-8)*(2b+8)=*2-
(2b-8)*(2b+8)=(*)2-
(18-m)*(18+m)=-2
(z-18)*(z+18)=2-
(18-cd)*(cd+18)=-()2
(8b-18)*(8b+18)=*2-
(8b-18)*(18+8b)=(*)2-
(2ab-zx)*(zx+2ab)=*()2-()2
(2z+a)*(a-2z)=2-*2
(mlu+2k)*(2k-mlu)=*2-()2
(18bc3-2x)*(2x+18bc3)=*b2c6-*2
(18bc3-2x)*(2x+18bc3)=(*bc3)2-*2