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

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

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

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

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

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

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

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

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

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

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

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

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

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

(3bc3-7x)*(7x+3bc3)=*b2c6-*2

(3bc3-7x)*(7x+3bc3)=(*bc3)2-*2



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