【WDSTC】評論
A^2-B^2=(A+B)(A-B)(A) 200.5^2-199.5^2=(200.5-199.5)(200.5+199.5)=1x400=400(B) 201.5^2-200.5^2=(201.5-200.5)(201.5+200.5)=1x402=402(C) 100.5^2-99.5^2=(100.5-99.5)(100.5+99.5)=1x200=200