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

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

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

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

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

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

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

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

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

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

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

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

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

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

(7bc3-4x)*(4x+7bc3)=*b2c6-*2

(7bc3-4x)*(4x+7bc3)=(*bc3)2-*2


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