0..1..4..9..16..25...求这个数列的第一项到第n项的求和,
来源:学生作业帮助网 编辑:作业帮 时间:2024/09/09 10:27:25
![0..1..4..9..16..25...求这个数列的第一项到第n项的求和,](/uploads/image/z/693820-28-0.jpg?t=0..1..4..9..16..25...%E6%B1%82%E8%BF%99%E4%B8%AA%E6%95%B0%E5%88%97%E7%9A%84%E7%AC%AC%E4%B8%80%E9%A1%B9%E5%88%B0%E7%AC%ACn%E9%A1%B9%E7%9A%84%E6%B1%82%E5%92%8C%2C)
xRJA ԛ;3O(>R? !dAHF``aÖ?ړmD!e=s8I%$EEKBbvP;nm>xnCՇKqyȨjR=,KIߣl.(0[;MjOj;`Uԙt4gUooHqz[NAH5I 3d$L
gC#0Tcư<4>s겦&jԴꗛP#6"~p i d83xAB,.Wzڸsc,lͥ %VhjXq\)˼v$BYh,,(p!#`iTp(ll磱4bvDضFǚrrå
F
0..1..4..9..16..25...求这个数列的第一项到第n项的求和,
0..1..4..9..16..25...求这个数列的第一项到第n项的求和,
0..1..4..9..16..25...求这个数列的第一项到第n项的求和,
因为an=(n-1)²
Sn=0+1+2²+3²+.+(n-1)²
又n³=(n-1+1)³=(n-1)³+3(n-1)²+3(n-1)+1
所以n³-(n-1)³=3(n-1)²+3(n-1)+1
即:
1³-0³=3*0²+3*0+1
2³-1³=3*1²+3*1+1
3³-2³=3*2²+3*2+1
.
n³-(n-1)³=3(n-1)²+3(n-1)+1
把以上各式累加得:
n³-0³=3[0²+1²+2²+.+(n-1)²]+3[1+2+3+.(n-1)]+n
即n³=3Sn+(3/2)n(n-1)+n
所以Sn=(2n³-3n²+n)/6=n(n-1)(2n-1)/6
36..49..64..81..0+1=1+3=4+5=9+7=16+9=25+11=36+13=49以此类推,每过一项多加2
规律an=(n-1)²
0..1..4..9..16..25...求这个数列的第一项到第n项的求和,
英语翻译1.sunday 2.never 3.early 4.on 5.sometimes 6.stay 7.til 8.lunchtime 9.late 10.dark 11.outside 12.what 13.thought 14.raining 15.telephone 16.rang 17.lucy 18.'I've 19.a'rrived 20.by 21.train 22.coming 23.still 24.having 25.bieakfast 26.asked
写出下列动词的过去式和过去分词:1.teach 2.sleep 3.think 4.build 5.dig 6.feel 7.find 8.get 9.hang 10.have 11.hold 12.hear 13.keep 14.learn 15.leave 16.come 17.become 18.run 19.be 20.do 21.sing 22.go 23.fall 24.fly 25.forget 26.freeze 2
急求动词的过去式(不规则)注上音标1.beat 2.begin 3.blow 4.break 5.bring 6.can 7.choose 8.cost 9.feel 10.fly 11.forget 12.freeze 13.fight 14.grow 15.hang 16.hide 17.hit 18.hurt 19.keep 20.know 21.learn 22.let 23.lie 24.may 25.mistake 26
写出下列名词的复数形式,1.bus 2.class 3.dress 4.piano 5.family 6.half 7.sheep 8.deer 9.lity 10.woman 11.foot 12.life 13.watch 14.radio 15.match 16.chinese 17.child 18.tomato 19.box 20.mouse 21.day 22.country 23.leaf 24twin broyher 25.woman
英语翻译1.lie 2.leave 3.proud 4.quarter 5.magazine 6.restaurant 7.wash 8.forest 9.feel 10.trip 11.wear 12.postcard 13.police 14.robbery 15.sound 16.program 17.congratulation 18.heavy 19.novel 20.quite 21.quiet 22.rise 23.chess 24.hard 25.factory
关于小学英语过去式写出下列动词的过去式;1.let 2.begin 3.put 4.ride 5.teach 6.feel 7.throw 8.keep 9.become 10meet 11.blow 12.cost 13.come 14.dig 15.sleep.16.drink 17.take18.feed 19.think 20.forge 21.give 22.wear 23.have.24.make 25.
英语 将下列词变为ing形式1.ask 2.look 3.carry 4.close 5.take 5.ride 6.swim 7.get 8.sit 9.put 10.begin 11.sleep 12.put 13.sing 14.meet 15.play 16.throw 17.draw 18.open 19.ride20.have 21.give 22.see 23.sit 24.run 25.lie 26.tie 27.die 28.listen
改变下列单词中的一个字母,使其成为另一个单词.1.at 2.bad 3.Let 4.now 5.dear 6.may 7.light 8.those 9.bee 10.in 11.that 12.so 13.same 14.purse 15.bus 16.bead 17.ill 18.toy 19.wall 20.we 21.make 22.the 23.like 24.mine 25.map
把下面的单数变为复数1.NOSE 2.EYE 3.HEAD 4.FACE 5.EAR 6.MOUTH 7.GIRL 8.BOY 9.MOVIE 10.STAR 11.CHINESE 12.ARM 13.LEG 14.FOOT 15.STUDENT 16.SISTER17.KNIFE 18.LETTER 19.MAN 20.WOMAN 21.SNOWMAN 22.T-SHIRT 23.SHOE24.CAP 25.COAT 26.SKIRT 27.DRESS
写出下列单词的音标1.pot 2.so 3.bike 4.bee 5.desk 6.in 7.kite 8.no 9.beg 10.dust 11.not 12.bus 13.egg 14.duty 15.home 16.box 17.see 18.hill 19.take 20.sad 21.go 22.tide 23.cut 24.us 25.like 26.he 27.not 28.fuse 29.
写出下列单词的音标1.pot 2.so 3.bike 4.bee 5.desk 6.in 7.kite 8.no 9.beg 10.dust 11.not 12.bus 13.egg 14.duty 15.home 16.box 17.see 18.hill 19.take 20.sad 21.go 22.tide 23.cut 24.us 25.like 26.he 27.not 28.fuse 29.use
化学27个元素 符号和字都要快点 要背 忘带书了```是这些字母 1.H 2.He 3.C 4.N 5.O 6.F7.Ae 8.Na 9.Mg 10.Al 11.Si 12.P 13.S 14.Cl 15.Ar 16.K 17.Ca 18.Mn 19.Fe 20.Cu 21.Zn 22.Ag 23.Ba 24.Pt 25.Au 26.Hg 27.I 汉字的
英语以下字母所代表的含义:1.UK 2.USA 3.SARS 4.NBA 5.PLA 6.PRC 7.PC 8.HK 9.VOA 10.IOC 11.KFC 12.AIDS 13.FIFA 14.DNA 15.IQ 16.PE 17.VIP 18.DDD 19.IT 20.RMB 21.EMS 22.ID 23.CCP 24.WTO 25.MTV 26.CAAC 27.P 请依次回答,写出题号,
谁知道下列英语简称的中文意思?1.BD 2.AD 3.CBA 4.CAAC 5.ABC 6.CBC 7.BA 8.HK 9.IBM 10.ID 11.MBA 12.PRC 13.CCP 14.PLA 15.PE 16.IQ 17.IOC 18.PC 19.IDD 20.EMS 21.IT 22.P.m 23.UNESCO 24.VIP 25.WTO 26.UK 27.USA 28.CAN如有错误请指出,
写出下列单词中元音字母的音标:1.cat 2.pat 3.sat 4.glad 5.clap 6.wrap 7.grade 8.late 9.make10.date 11.name 12.sale 13.me 14.she 15.he 16.these 17.let 18.bed 19.help 20.get 21.pen 22.red 23.set 24.wet 25.hi 26.mine 27.bike 28.life 29.bit
刚刚做了 epQ 测试题 分析出来 1.否 2.否 3.是 4.是 5.是 6.是 7.是 8.是 9.是 10.是11.是 12.是 13.否 14.是 15.是 16.是 17.否 18.是 19.是 20.否21.是 22.否 23.是 24.是 25.是 26.否 27.是 28.是 29.否 30.否 31.是 32.
周处 加点字解释1.少 2.凶强 3.侠气 4.为 5.乡 6.里 7.患 8.并 9.暴犯 10.谓为 11.横 12尤 13.剧 14.或 15.说 16.翼 17.唯 18.余 19.即 20.或 21.浮 22.没 23.行 24.数 25.与 26.惧 27.更 28.庆 29.竟 30.始 31.人情 32.乃