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

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

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

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

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

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

(18-m)*(18+m)=-2

(z-18)*(z+18)=2-

(18-cd)*(cd+18)=-()2

(2b-18)*(2b+18)=*2-

(2b-18)*(18+2b)=(*)2-

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

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

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

(18bc3-3x)*(3x+18bc3)=*b2c6-*2

(18bc3-3x)*(3x+18bc3)=(*bc3)2-*2


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