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

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

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

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

(3b-9)*(3b+9)=*2-

(3b-9)*(3b+9)=(*)2-

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

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

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

(9b-7)*(9b+7)=*2-

(9b-7)*(7+9b)=(*)2-

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

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

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

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

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


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