a2-b2=(a-b)(a+b)
(1-x)*(1+x)=-2
(a-1)*(a+1)=2-
(1-cd)*(1+cd)=-()2
(5b-1)*(5b+1)=*2-
(5b-1)*(5b+1)=(*)2-
(16-m)*(16+m)=-2
(z-16)*(z+16)=2-
(16-cd)*(cd+16)=-()2
(1b-16)*(1b+16)=*2-
(1b-16)*(16+1b)=(*)2-
(5ab-zx)*(zx+5ab)=*()2-()2
(5z+a)*(a-5z)=2-*2
(mlu+5k)*(5k-mlu)=*2-()2
(16bc3-5x)*(5x+16bc3)=*b2c6-*2
(16bc3-5x)*(5x+16bc3)=(*bc3)2-*2