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

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

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

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

(5b-4)*(5b+4)=*2-

(5b-4)*(5b+4)=(*)2-

(15-m)*(15+m)=-2

(z-15)*(z+15)=2-

(15-cd)*(cd+15)=-()2

(4b-15)*(4b+15)=*2-

(4b-15)*(15+4b)=(*)2-

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

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

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

(15bc3-5x)*(5x+15bc3)=*b2c6-*2

(15bc3-5x)*(5x+15bc3)=(*bc3)2-*2



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