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

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

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

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

(1b-7)*(1b+7)=*2-

(1b-7)*(1b+7)=(*)2-

(3-m)*(3+m)=-2

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

(3-cd)*(cd+3)=-()2

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

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

(1ab-zx)*(zx+1ab)=*()2-()2

(1z+a)*(a-1z)=2-*2

(mlu+1k)*(1k-mlu)=*2-()2

(3bc3-1x)*(1x+3bc3)=*b2c6-*2

(3bc3-1x)*(1x+3bc3)=(*bc3)2-*2


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