Question

1-2+3-4+5-6+.+2009-2010这道题怎样解,这道题的解题过程

Answer 1

1-2+3-4+5-6+.+2009-2010

=(1+3+5+.+2009)-(2+4+6+.-2010)

=[(1+2009)/2]×1005-[(2-2010)/2]×1005

=[(1+2009)/2-(2-2010)/2]×1005

=(1005-1006)]×1005

= -1005