1+(-2)+(+3)+(-4)+(+5)+...+(-2008)+(+2009)

来源:学生作业帮助网 编辑:作业帮 时间:2024/05/11 04:37:59
1+(-2)+(+3)+(-4)+(+5)+...+(-2008)+(+2009)

1+(-2)+(+3)+(-4)+(+5)+...+(-2008)+(+2009)
1+(-2)+(+3)+(-4)+(+5)+...+(-2008)+(+2009)

1+(-2)+(+3)+(-4)+(+5)+...+(-2008)+(+2009)
1+(-2)+(+3)+(-4)+^+(-2008)+(2009)
=1-2+3-4+^-2008+2009
=(1-2)+(3-4)+^+(2007-2008)+2009
=-1-1-1-1-^-1+2009
=-1004*1+2009
=1005