a2-b2=(a-b)(a+b)
(2-x)*(2+x)=-2
(a-2)*(a+2)=2-
(2-cd)*(2+cd)=-()2
(4b-2)*(4b+2)=*2-
(4b-2)*(4b+2)=(*)2-
(6-m)*(6+m)=-2
(z-6)*(z+6)=2-
(6-cd)*(cd+6)=-()2
(2b-6)*(2b+6)=*2-
(2b-6)*(6+2b)=(*)2-
(4ab-zx)*(zx+4ab)=*()2-()2
(4z+a)*(a-4z)=2-*2
(mlu+4k)*(4k-mlu)=*2-()2
(6bc3-4x)*(4x+6bc3)=*b2c6-*2
(6bc3-4x)*(4x+6bc3)=(*bc3)2-*2