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

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

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

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

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

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

(10-m)*(10+m)=-2

(z-10)*(z+10)=2-

(10-cd)*(cd+10)=-()2

(9b-10)*(9b+10)=*2-

(9b-10)*(10+9b)=(*)2-

(4ab-zx)*(zx+4ab)=*()2-()2

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

(mlu+4k)*(4k-mlu)=*2-()2

(10bc3-4x)*(4x+10bc3)=*b2c6-*2

(10bc3-4x)*(4x+10bc3)=(*bc3)2-*2



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