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

(4-x)*(4+x)=-2

(a-4)*(a+4)=2-

(4-cd)*(4+cd)=-()2

(7b-4)*(7b+4)=*2-

(7b-4)*(7b+4)=(*)2-

(9-m)*(9+m)=-2

(z-9)*(z+9)=2-

(9-cd)*(cd+9)=-()2

(4b-9)*(4b+9)=*2-

(4b-9)*(9+4b)=(*)2-

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

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

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

(9bc3-7x)*(7x+9bc3)=*b2c6-*2

(9bc3-7x)*(7x+9bc3)=(*bc3)2-*2



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