Question

1-2+3-4+5-6+....2005-2006+2007-2008+2009=

Answer 1

1-2+3-4+5-6+....2005-2006+2007-2008+2009
=（1-2）+（3-4）+（5-6）+....(2005-2006)+(2007-2008)+2009
=-1-1-1-...-1+2009
=-1x2008/2+2009
=-1004+2009
=1005

Answer 2

原式=-1+(-1)+(-1)...+2009
=-1*1004+2009
=-1004+2009
=1005

Answer 3

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

Answer 4

(1-2)+(3-4)+(5-6)+....(2005-2006)+(2007-2008)+2009
=(-1)×(2008/2)+2009
=-1004+2009=1005

Answer 5

=(1+3+5+...+2007+2009)-(2+4+6+...+2006+2008)
=(1+2009)/2*[(2009-1)/2+1]-(2+2008)/2*{(2008-2)/2+1]
=1500*1005-1500*1004
=1500

Answer 6

1005