a2-b2=(a-b)(a+b)
(5-x)*(5+x)=-2
(a-5)*(a+5)=2-
(5-cd)*(5+cd)=-()2
(4b-5)*(4b+5)=*2-
(4b-5)*(4b+5)=(*)2-
(3-m)*(3+m)=-2
(z-3)*(z+3)=2-
(3-cd)*(cd+3)=-()2
(5b-3)*(5b+3)=*2-
(5b-3)*(3+5b)=(*)2-
(4ab-zx)*(zx+4ab)=*()2-()2
(4z+a)*(a-4z)=2-*2
(mlu+4k)*(4k-mlu)=*2-()2
(3bc3-4x)*(4x+3bc3)=*b2c6-*2
(3bc3-4x)*(4x+3bc3)=(*bc3)2-*2