a2-b2=(a-b)(a+b)
(8-x)*(8+x)=-2
(a-8)*(a+8)=2-
(8-cd)*(8+cd)=-()2
(5b-8)*(5b+8)=*2-
(5b-8)*(5b+8)=(*)2-
(4-m)*(4+m)=-2
(z-4)*(z+4)=2-
(4-cd)*(cd+4)=-()2
(8b-4)*(8b+4)=*2-
(8b-4)*(4+8b)=(*)2-
(5ab-zx)*(zx+5ab)=*()2-()2
(5z+a)*(a-5z)=2-*2
(mlu+5k)*(5k-mlu)=*2-()2
(4bc3-5x)*(5x+4bc3)=*b2c6-*2
(4bc3-5x)*(5x+4bc3)=(*bc3)2-*2