1-2+3-4+5-6+7-8···-1998+1

1-2+3-4+5-6+7-8···-1998+1999=1000 计算过程是什么?重谢!

5个回答

(1-2)+(3-4)+(5-6)+……（1997-1998）+1999
=-1+ -1+ -1 +……+ -1 + 1999
=-999+1999
=1000