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

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

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

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

(6b-7)*(6b+7)=*2-

(6b-7)*(6b+7)=(*)2-

(11-m)*(11+m)=-2

(z-11)*(z+11)=2-

(11-cd)*(cd+11)=-()2

(7b-11)*(7b+11)=*2-

(7b-11)*(11+7b)=(*)2-

(6ab-zx)*(zx+6ab)=*()2-()2

(6z+a)*(a-6z)=2-*2

(mlu+6k)*(6k-mlu)=*2-()2

(11bc3-6x)*(6x+11bc3)=*b2c6-*2

(11bc3-6x)*(6x+11bc3)=(*bc3)2-*2


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