Math question!

2007-2006+2005-2004 +..........+9-8
= 2007-2006+2005-2004+......+9-8+(7-6+5-4+3-2+1) - (7-6+5-4+3-2+1)
= (2007-2006)+(2005-2004)+...+(3-2)+1 -( (7-6) + (5-4) + (3-2) +1 )
= 1 x (2006/2) +1 - ( 1 x (6/2) +1)
= 1003 + 1 - 3 - 1
= 1000

2008-04-03 15:04:07 補充：
(2007-2006)+(2005-2004)+...+(3-2)+1 這個組合的計法可看看(7-6) + (5-4) + (3-2) +1.

2007-2006+2005-2004 +..........+9-8
=(2007-2006)+(2005-2004) +..........+(9-8)
=1+1+...+1 (1000 個)
=1000

2008-04-03 15:03:10 補充：
因為(2007+1-8)/2=1000 所以共有1000個