计算:1-2+3-4+…+2007-2008+2009=_.
问题描述:
计算:1-2+3-4+…+2007-2008+2009=______.
答
1-2+3-4+…+2007-2008+2009
=1+[(3-2)+(5-4)+…+(2009-2008)]
=1+1004
=1005
故答案为:1005.