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

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

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

(1-cd)*(1+cd)=-()2

(3b-1)*(3b+1)=*2-

(3b-1)*(3b+1)=(*)2-

(19-m)*(19+m)=-2

(z-19)*(z+19)=2-

(19-cd)*(cd+19)=-()2

(1b-19)*(1b+19)=*2-

(1b-19)*(19+1b)=(*)2-

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

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

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

(19bc3-3x)*(3x+19bc3)=*b2c6-*2

(19bc3-3x)*(3x+19bc3)=(*bc3)2-*2


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