绝对值计算:|1／1001-1／1000| + |1／1002-1／1001| + |1／1002+ 1／1000|

这题超简单啊,分数的分子相同时,分母越小,值越大.
所以:
1/1000>1/1001>1/1002

1/1001-1/1000<0
1/1002-1/1001<0

|1／1001-1／1000|=1/1000-1/1001
|1／1002-1／1001|=1/1001-1/1002

去掉绝对值,得:
1/1000-1/1001+1/1001-1/1002+1/1002+1/1000
=1/1000+1/1000
=1/500

1/500