a2-b2=(a-b)(a+b)

(7-x)*(7+x)=-2

(a-7)*(a+7)=2-

(7-cd)*(7+cd)=-()2

(9b-7)*(9b+7)=*2-

(9b-7)*(9b+7)=(*)2-

(16-m)*(16+m)=-2

(z-16)*(z+16)=2-

(16-cd)*(cd+16)=-()2

(7b-16)*(7b+16)=*2-

(7b-16)*(16+7b)=(*)2-

(9ab-zx)*(zx+9ab)=*()2-()2

(9z+a)*(a-9z)=2-*2

(mlu+9k)*(9k-mlu)=*2-()2

(16bc3-9x)*(9x+16bc3)=*b2c6-*2

(16bc3-9x)*(9x+16bc3)=(*bc3)2-*2


×