3-5+7-9..............................+1999-2001+2003=?
(列出ㅡ步步方法更佳)
急需(10分)
2007-10-11 10:08 pm
回答 (2)
2007-10-11 10:27 pm
✔ 最佳答案
3-5+7-9..............................+1999-2001+2003= (3-5) + (7-9) + (11-13) +..............................+ (1999-2001) +2003
= (-2) + (-2) + (-2) +....................+ (-2) + 2003
= {[(1999-3)/4]+1}*(-2) + 2003 ------------(前面果個係計有幾多個負二)
= 500*(-2) + 2003
= -1000 + 2003
= 1003
2007-10-11 10:12 pm
3+7+11+.......+1999+2003=x
5+9+13+....+1997+2001=y
x-y=??
2007-10-11 14:17:49 補充：
x=(2003+3)X(<2003-3>/4)/2=2006X500/2y=(2001+5)X(<2001-5>/4)/2=2006X499/2x-y=2006X(500-499)/2=1003
5+9+13+....+1997+2001=y
x-y=??
2007-10-11 14:17:49 補充：
x=(2003+3)X(<2003-3>/4)/2=2006X500/2y=(2001+5)X(<2001-5>/4)/2=2006X499/2x-y=2006X(500-499)/2=1003
收錄日期: 2021-04-13 13:51:45
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071011000051KK01211