a2-b2=(a-b)(a+b)
(2-x)*(2+x)=-2
(a-2)*(a+2)=2-
(2-cd)*(2+cd)=-()2
(5b-2)*(5b+2)=*2-
(5b-2)*(5b+2)=(*)2-
(11-m)*(11+m)=-2
(z-11)*(z+11)=2-
(11-cd)*(cd+11)=-()2
(2b-11)*(2b+11)=*2-
(2b-11)*(11+2b)=(*)2-
(5ab-zx)*(zx+5ab)=*()2-()2
(5z+a)*(a-5z)=2-*2
(mlu+5k)*(5k-mlu)=*2-()2
(11bc3-5x)*(5x+11bc3)=*b2c6-*2
(11bc3-5x)*(5x+11bc3)=(*bc3)2-*2