a2-b2=(a-b)(a+b)
(5-x)*(5+x)=-2
(a-5)*(a+5)=2-
(5-cd)*(5+cd)=-()2
(6b-5)*(6b+5)=*2-
(6b-5)*(6b+5)=(*)2-
(12-m)*(12+m)=-2
(z-12)*(z+12)=2-
(12-cd)*(cd+12)=-()2
(5b-12)*(5b+12)=*2-
(5b-12)*(12+5b)=(*)2-
(6ab-zx)*(zx+6ab)=*()2-()2
(6z+a)*(a-6z)=2-*2
(mlu+6k)*(6k-mlu)=*2-()2
(12bc3-6x)*(6x+12bc3)=*b2c6-*2
(12bc3-6x)*(6x+12bc3)=(*bc3)2-*2