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

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

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

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

(5b-7)*(5b+7)=*2-

(5b-7)*(5b+7)=(*)2-

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

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

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

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

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

(5ab-zx)*(zx+5ab)=*()2-()2

(5z+a)*(a-5z)=2-*2

(mlu+5k)*(5k-mlu)=*2-()2

(2bc3-5x)*(5x+2bc3)=*b2c6-*2

(2bc3-5x)*(5x+2bc3)=(*bc3)2-*2


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