a2-b2=(a-b)(a+b)
(4-x)*(4+x)=-2
(a-4)*(a+4)=2-
(4-cd)*(4+cd)=-()2
(9b-4)*(9b+4)=*2-
(9b-4)*(9b+4)=(*)2-
(14-m)*(14+m)=-2
(z-14)*(z+14)=2-
(14-cd)*(cd+14)=-()2
(4b-14)*(4b+14)=*2-
(4b-14)*(14+4b)=(*)2-
(9ab-zx)*(zx+9ab)=*()2-()2
(9z+a)*(a-9z)=2-*2
(mlu+9k)*(9k-mlu)=*2-()2
(14bc3-9x)*(9x+14bc3)=*b2c6-*2
(14bc3-9x)*(9x+14bc3)=(*bc3)2-*2