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-

(17-m)*(17+m)=-2

(z-17)*(z+17)=2-

(17-cd)*(cd+17)=-()2

(7b-17)*(7b+17)=*2-

(7b-17)*(17+7b)=(*)2-

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

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

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

(17bc3-3x)*(3x+17bc3)=*b2c6-*2

(17bc3-3x)*(3x+17bc3)=(*bc3)2-*2


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