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

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

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

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

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

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

(10-m)*(10+m)=-2

(z-10)*(z+10)=2-

(10-cd)*(cd+10)=-()2

(7b-10)*(7b+10)=*2-

(7b-10)*(10+7b)=(*)2-

(7ab-zx)*(zx+7ab)=*()2-()2

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

(mlu+7k)*(7k-mlu)=*2-()2

(10bc3-7x)*(7x+10bc3)=*b2c6-*2

(10bc3-7x)*(7x+10bc3)=(*bc3)2-*2


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