a2-b2=(a-b)(a+b)
(6-x)*(6+x)=-2
(a-6)*(a+6)=2-
(6-cd)*(6+cd)=-()2
(6b-6)*(6b+6)=*2-
(6b-6)*(6b+6)=(*)2-
(11-m)*(11+m)=-2
(z-11)*(z+11)=2-
(11-cd)*(cd+11)=-()2
(6b-11)*(6b+11)=*2-
(6b-11)*(11+6b)=(*)2-
(6ab-zx)*(zx+6ab)=*()2-()2
(6z+a)*(a-6z)=2-*2
(mlu+6k)*(6k-mlu)=*2-()2
(11bc3-6x)*(6x+11bc3)=*b2c6-*2
(11bc3-6x)*(6x+11bc3)=(*bc3)2-*2