1/1x4x7+1/2x5x8+1/3x6x9+……+1/n(n+3)(n+6)=?
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解决时间 2021-11-08 09:40
- 提问者网友：伴风望海
- 2021-11-08 00:42
1/1x4x7+1/2x5x8+1/3x6x9+……+1/n(n+3)(n+6)=?
最佳答案
- 五星知识达人网友：梦中风几里
- 2021-11-08 02:15
an
=1/[n(n+3)(n+6)]
=(1/6) { 1/[n(n+3)] - 1/[(n+3)(n+6)] }
Sn
= a1+a2+...+an
=(1/6) { 1/4 - 1/[(n+3)(n+6)] }
1/(1x4x7)+1/(2x5x8)+1/(3x6x9)+……+1/[n(n+3)(n+6)]
=Sn
=(1/6) { 1/4 - 1/[(n+3)(n+6)] }追问好象不对，你自己验证一下?追答不好意思！
an
=1/[n(n+3)(n+6)]
=(1/6) { 1/[n(n+3)] - 1/[(n+3)(n+6)] }
Sn
= a1+a2+...+an
=(1/6) { 1/(1x4) + 1/(2x5) +1/(3x6) -1/[(n+1)(n+4)] -1/[(n+2)(n+5)] - 1/[(n+3)(n+6)] }
1/(1x4x7)+1/(2x5x8)+1/(3x6x9)+……+1/[n(n+3)(n+6)]
=Sn
=(1/6) { 1/(1x4) + 1/(2x5) +1/(3x6) -1/[(n+1)(n+4)] -1/[(n+2)(n+5)] - 1/[(n+3)(n+6)] }追问非常感谢，大脑灵活，采纳！
=1/[n(n+3)(n+6)]
=(1/6) { 1/[n(n+3)] - 1/[(n+3)(n+6)] }
Sn
= a1+a2+...+an
=(1/6) { 1/4 - 1/[(n+3)(n+6)] }
1/(1x4x7)+1/(2x5x8)+1/(3x6x9)+……+1/[n(n+3)(n+6)]
=Sn
=(1/6) { 1/4 - 1/[(n+3)(n+6)] }追问好象不对，你自己验证一下?追答不好意思！
an
=1/[n(n+3)(n+6)]
=(1/6) { 1/[n(n+3)] - 1/[(n+3)(n+6)] }
Sn
= a1+a2+...+an
=(1/6) { 1/(1x4) + 1/(2x5) +1/(3x6) -1/[(n+1)(n+4)] -1/[(n+2)(n+5)] - 1/[(n+3)(n+6)] }
1/(1x4x7)+1/(2x5x8)+1/(3x6x9)+……+1/[n(n+3)(n+6)]
=Sn
=(1/6) { 1/(1x4) + 1/(2x5) +1/(3x6) -1/[(n+1)(n+4)] -1/[(n+2)(n+5)] - 1/[(n+3)(n+6)] }追问非常感谢，大脑灵活，采纳！
全部回答
- 1楼网友：西风乍起
- 2021-11-08 03:51
xxxx
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