1×4+2×5+3×6......40×43 怎麼算
回答 (2)
2012-02-04 4:54 am
✔ 最佳答案
1×4+2×5+3×6......40×43 怎麼算Sol
1*4+2*5+3*6+…+40*43
=Σ(k=1 to 40)_k*(k+3)
=Σ(k=1 to 40)_k^2+Σ(k=1 to 40)_3
=40*(40+1)*(2*40+1)/6+3*40
=22140+120
=22260
2012-02-07 6:03 am
=Σ(k=1 to 40)_k*(k+3)
=Σ(k=1 to 40)_k^2+Σ(k=1 to 40)_3
應該是 3k
=Σ(k=1 to 40)_k^2+Σ(k=1 to 40)_3
應該是 3k
收錄日期: 2021-04-30 16:23:51
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120203000010KK08592