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

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

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

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

(3b-7)*(3b+7)=*2-

(3b-7)*(3b+7)=(*)2-

(8-m)*(8+m)=-2

(z-8)*(z+8)=2-

(8-cd)*(cd+8)=-()2

(7b-8)*(7b+8)=*2-

(7b-8)*(8+7b)=(*)2-

(3ab-zx)*(zx+3ab)=*()2-()2

(3z+a)*(a-3z)=2-*2

(mlu+3k)*(3k-mlu)=*2-()2

(8bc3-3x)*(3x+8bc3)=*b2c6-*2

(8bc3-3x)*(3x+8bc3)=(*bc3)2-*2


×