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

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

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

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

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

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

(1-m)*(1+m)=-2

(z-1)*(z+1)=2-

(1-cd)*(cd+1)=-()2

(4b-1)*(4b+1)=*2-

(4b-1)*(1+4b)=(*)2-

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

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

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

(1bc3-2x)*(2x+1bc3)=*b2c6-*2

(1bc3-2x)*(2x+1bc3)=(*bc3)2-*2



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