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

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

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

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

(5b-9)*(5b+9)=*2-

(5b-9)*(5b+9)=(*)2-

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

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

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

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

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

(5ab-zx)*(zx+5ab)=*()2-()2

(5z+a)*(a-5z)=2-*2

(mlu+5k)*(5k-mlu)=*2-()2

(3bc3-5x)*(5x+3bc3)=*b2c6-*2

(3bc3-5x)*(5x+3bc3)=(*bc3)2-*2



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