a2-b2=(a-b)(a+b)
(8-x)*(8+x)=-2
(a-8)*(a+8)=2-
(8-cd)*(8+cd)=-()2
(4b-8)*(4b+8)=*2-
(4b-8)*(4b+8)=(*)2-
(7-m)*(7+m)=-2
(z-7)*(z+7)=2-
(7-cd)*(cd+7)=-()2
(8b-7)*(8b+7)=*2-
(8b-7)*(7+8b)=(*)2-
(4ab-zx)*(zx+4ab)=*()2-()2
(4z+a)*(a-4z)=2-*2
(mlu+4k)*(4k-mlu)=*2-()2
(7bc3-4x)*(4x+7bc3)=*b2c6-*2
(7bc3-4x)*(4x+7bc3)=(*bc3)2-*2