3-4+5-6+...+2001-200+2003-2004+2005
问题描述:
3-4+5-6+...+2001-200+2003-2004+2005
答
3-4+5-6+...+2001-2002+2003-2004+2005
=(3-4)+(5-6)+...+(2001-2002)+(2003-2004)+2005
= -1+(-1)+.+(-1)+2005
= -[(2003-3)/2 +1]+2005
=-1001+2005
=1004