1+2+3+4+5+6+7+8+9+9+8+7+5+6+4+3+2+1
回答 (11)
2007-03-16 5:40 am
✔ 最佳答案
1+2+3+4+5+6+7+8+9+9+8+7+5+6+4+3+2+1 =45(2)
=90
2007-03-15 21:43:30 補充：
(1+2+3+4+5+6+7+8+9)2=(45)2=90(1+2+3+4+5+6+7+8+9) = (1+9)+(2+8)+(7+3)+(4+6)+5 = 10(4)+5
參考: me
2007-03-18 2:53 am
1+2+3+4+5+6+7+8+9+9+8+7+5+6+4+3+2+1
＝45＋45
＝90
＝45＋45
＝90
2007-03-17 7:31 am
1+2+3+4+5+6+7+8+9+9+8+7+5+6+4+3+2+1
=(1+9)(9)/2 + (1+9)(9)/2
=(1+9)(9)
=90
By
1+2+3+4+5+.............+N
=(1+N)(N)/2
=(1+9)(9)/2 + (1+9)(9)/2
=(1+9)(9)
=90
By
1+2+3+4+5+.............+N
=(1+N)(N)/2
參考: me
2007-03-17 12:23 am
因為1+2+3+4+5+6+7+8+9+8+7+6+5+4+3+2+1=9^2
SO 1+2+3+4+5+6+7+8+9+9+8+7+6+5+4+3+2+1 =9^2+9
=81+9
=90
SO 1+2+3+4+5+6+7+8+9+9+8+7+6+5+4+3+2+1 =9^2+9
=81+9
=90
2007-03-17 12:03 am
1+2+3+......+(n-1)+n+n+(n-1)+(n-2)+.......+3+2+1
=(1+n)n
1+2+3+4+5+6+7+8+9+9+8+7+6+5+4+3+2+1
=(1+9)9
=90
=(1+n)n
1+2+3+4+5+6+7+8+9+9+8+7+6+5+4+3+2+1
=(1+9)9
=90
2007-03-16 9:42 am
=(1+2+3+4+5+6+7+8+9)+(9+8+7+5+6+4+3+2+1)
=(1+9)*9/2+(1+9)*9/2
=2*(1+9)*9/2
=(1+9)*9
=10*9
=90
=(1+9)*9/2+(1+9)*9/2
=2*(1+9)*9/2
=(1+9)*9
=10*9
=90
2007-03-16 6:04 am
咪係９０lo~~~
2007-03-16 5:42 am
1+2+3+4+5+6+7+8+9+9+8+7+5+6+4+3+2+1
=90囉
=90囉
收錄日期: 2021-04-12 18:46:16
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070315000051KK04466