math problem math problem
2012-07-06 2:04 am
find the sum of terms in arithmetic sequences
1,3,5...(2n-1)~~~can i use (first term+last term)(項數)/2???but wt is 項數@@?
回答 (2)
2012-07-06 3:53 am
✔ 最佳答案
common difference=3-1
=2
T(n)=1+(n-1)(2)
=2n-1
number of terms=n
S(n)=n(1+2n-1)/2
=n^2
參考: me
2012-07-06 3:52 am
項數 = (last term - first term)/(common difference) + 1
SO
項數 = (2n - 1 - 1)/2 + 1 = n
SO
項數 = (2n - 1 - 1)/2 + 1 = n
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