(1+3+5+7+9+11+~+2007+2009)-(2+4+6+8+10+~+2006+2008)
=1-2+3-4+5-6+7-8+~+2007-2008+2009
=(1-2)+(3-4)+(5-6)+~+(2007-2008)+2009
=(-1)+(-1)+(-1)+~+(-1)+2009
=(-1)*1004+2009
=-1004+2009
=1005
希望参考!+-+
(1+3+5+7+9+11+~+2007+2009)-(2+4+6+8+10+~+2006+2008)
=1-2+3-4+5-6+7-8+~+2007-2008+2009
=(1-2)+(3-4)+(5-6)+~+(2007-2008)+2009
=(-1)+(-1)+(-1)+~+(-1)+2009
=(-1)*1004+2009
=-1004+2009
=1005
希望参考!+-+