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3(1+2+3+...+32+33)=3*(1+33)*33/2=3*34*33/2=3*33*17=(100-1)*17=1700-17=1683 中小學生的問題吧 補充一下設s=1 + 2 + 3 +...+ 31 + 32 + 33則s=33+ 32 + 31 +...+ 3 + 2 + 12s=(1+33)+(2+32)+(3+31)+...(31+...
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