a2-b2=(a-b)(a+b)
(6-x)*(6+x)=-2
(a-6)*(a+6)=2-
(6-cd)*(6+cd)=-()2
(4b-6)*(4b+6)=*2-
(4b-6)*(4b+6)=(*)2-
(17-m)*(17+m)=-2
(z-17)*(z+17)=2-
(17-cd)*(cd+17)=-()2
(6b-17)*(6b+17)=*2-
(6b-17)*(17+6b)=(*)2-
(4ab-zx)*(zx+4ab)=*()2-()2
(4z+a)*(a-4z)=2-*2
(mlu+4k)*(4k-mlu)=*2-()2
(17bc3-4x)*(4x+17bc3)=*b2c6-*2
(17bc3-4x)*(4x+17bc3)=(*bc3)2-*2