求(2+5+8······+2000)-(1+4+7······+1999)的值.【简算】

问题描述:

求(2+5+8······+2000)-(1+4+7······+1999)的值.【简算】

667

(2+5+8······+2000)-(1+4+7······+1999)
=(2-1)+(5-4)+(8-7)+。。。。+(2000-1999)
=1+1+。。。+1 (共667个1)
=667

很简单.
(2+5+8······+2000)-(1+4+7······+1999)
=(2-1)+(5-4)+(8-7)+.+(2000-1999)【一共有667个组合
=1+1+…+1 因此这有667个1】
=667
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