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

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

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

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

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

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

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

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

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

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

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

(1ab-zx)*(zx+1ab)=*()2-()2

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

(mlu+1k)*(1k-mlu)=*2-()2

(7bc3-1x)*(1x+7bc3)=*b2c6-*2

(7bc3-1x)*(1x+7bc3)=(*bc3)2-*2


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