a2-b2=(a-b)(a+b)
(3-x)*(3+x)=-2
(a-3)*(a+3)=2-
(3-cd)*(3+cd)=-()2
(2b-3)*(2b+3)=*2-
(2b-3)*(2b+3)=(*)2-
(11-m)*(11+m)=-2
(z-11)*(z+11)=2-
(11-cd)*(cd+11)=-()2
(3b-11)*(3b+11)=*2-
(3b-11)*(11+3b)=(*)2-
(2ab-zx)*(zx+2ab)=*()2-()2
(2z+a)*(a-2z)=2-*2
(mlu+2k)*(2k-mlu)=*2-()2
(11bc3-2x)*(2x+11bc3)=*b2c6-*2
(11bc3-2x)*(2x+11bc3)=(*bc3)2-*2