a2-b2=(a-b)(a+b)
(5-x)*(5+x)=-2
(a-5)*(a+5)=2-
(5-cd)*(5+cd)=-()2
(8b-5)*(8b+5)=*2-
(8b-5)*(8b+5)=(*)2-
(19-m)*(19+m)=-2
(z-19)*(z+19)=2-
(19-cd)*(cd+19)=-()2
(5b-19)*(5b+19)=*2-
(5b-19)*(19+5b)=(*)2-
(8ab-zx)*(zx+8ab)=*()2-()2
(8z+a)*(a-8z)=2-*2
(mlu+8k)*(8k-mlu)=*2-()2
(19bc3-8x)*(8x+19bc3)=*b2c6-*2
(19bc3-8x)*(8x+19bc3)=(*bc3)2-*2