1. n!(n+2)!
______________
(n+1)!(n+3)!
[直線係分數線]
AMATHS的bio題目一條
2007-09-30 8:42 pm
回答 (2)
2007-09-30 9:50 pm
✔ 最佳答案
1. n!(n+2)! / (n+1)!(n+3)!n!(n+2)! / (n+1)!(n+3)!
= n!(n+2)! / (n+1)(n!)(n+3)(n+2)!
= 1/ (n+1)(n+3)
2.1/n! - 1/(n+1)!
1/n! - 1/(n+1)!
= 1/n! - 1/(n+1)(n!)
= (n+1) -1/(n+1)(n!)
= n / (n+1)!
2007-09-30 13:51:35 補充：
樓上:其實你唔需要expand佢
2007-09-30 8:54 pm
n!(n+2)!
----------------
(n+1)!(n+3)!
n!(n+2)!
=-------------------------------
n!*(n+1)*(n+2)!*(n+3)
1
=-----------------
(n+1)*(n+3)
1
=----------------
(n^2+4n+3)
I hope this can help your understanding. =)
2007-10-01 15:42:10 補充：
1/n! - 1/(n+1)!=(n+1)/(n+1)! - 1/(n+1)!=(n+1-1)/(n+1)!= n / (n+1)!
----------------
(n+1)!(n+3)!
n!(n+2)!
=-------------------------------
n!*(n+1)*(n+2)!*(n+3)
1
=-----------------
(n+1)*(n+3)
1
=----------------
(n^2+4n+3)
I hope this can help your understanding. =)
2007-10-01 15:42:10 補充：
1/n! - 1/(n+1)!=(n+1)/(n+1)! - 1/(n+1)!=(n+1-1)/(n+1)!= n / (n+1)!
參考: Myself ^^
收錄日期: 2021-04-13 13:42:17
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070930000051KK01793