,
,其中n∈N+ . (I)求证:数列{bn}是等差数列,并求出数列{an}的通项公式;
(II)设
,求数列{cncn+2}的前n项和为Tn .
梦
张 洁
①现在想起来,仿佛已是很遥远的事情了。在我很小的时候,我常梦见我在溜冰场上大显神通,像陀螺般旋转,像流星般飞驰,像燕子掠水般滑翔。我也梦见过在海浪里嬉戏,跃上浪尖,纵入浪谷。其实我既不会滑冰也不会游泳。我甚至连海也没有见过,而且那个时候我连冰鞋也买不起一双。我还梦见过我既是我自己又不是我自己,我是那样的端庄妩媚,仪态万方,完全不像现实生活中那样畏缩、灰暗……在梦里,我扮演过多少在我醒时渴望着的美好角色,做出过许许多多毕竟是异想天开的事情。
②前些日子,我梦见我重回少年时代生长过的地方。那山坳、那流水、那树林,宛如我曾爱过的一样。可是,当我张开双臂,扑进那树林里去的时候,我发现,我已经不认识它了。
③树木都已长大,再也找不到儿时的痕迹。我怅然地在那树林里徘徊,用手掌抚摸着每一棵树的树干,懊悔着自己曾被那许多微不足道的理由所羁绊,而在这样久的时间里,丢失了我曾爱过的这山坳、这流水、这树木……我还能追捕回来这许多年里所丢失的欢乐吗?人有时是多么愚蠢、多么迟钝!又是多么地苦着自己、折磨着自己啊!
④我喃喃地对那树林低语:看看我,还认得我吗?我是大雁啊!原谅我过了这许多年才飞回来看你,尽管我已经没有多少力气,尽管我翅膀上那些曾经美丽的翎羽已经所剩无几,可我毕竟带着一颗从未忘怀的心回来了!
⑤风儿刮起来了,所有的树木全都摇曳着它们的枝丫。树叶儿飒飒地响起来了,我听懂了它们的絮语:不,我们不认识你,你不是大雁,必不是她!她不是这样长满皱纹的,她的心上也不是这样落满尘埃的!
⑥啊,岁月和生活就是这样改变了它们和我,我们不再互相认识了。
⑦我感到累极了。我能不累吗?真的,我早已不是那只蹦蹦跳跳的小山羊。于是,长叹一声,我躺在长满野草的山坡上。
⑧变幻的云朵,悠悠地从我的头上飘过。我重又看见在童年的幻觉中出现过的神话:骏马拖着的彩车,飘飘欲仙的美女,富丽堂皇的宫殿……我的心突然变得甜蜜,在那云朵里,我好像看见了童年时代的自己,那曾是可爱的小姑娘,光着脚丫,吧嗒、吧嗒地向我跑来,带着用毛笔勾画的眼镜,还有毛笔勾画的皱纹和胡须,张开没有门牙的嘴巴,嘎嘎地笑着,并且对我说:“你这傻老太婆,为什么要找我呢?我并没有离开你,我一直住在你心里。不然,你何以有一颗儿童的心呢?”
⑨天哪!天哪!毕竟还有人认得我啊!
⑩她笑着,从我的身旁飞快地跑过。跳过小溪,跑进树林里去。浅蓝色的衣裙在树干后面闪动着,留下了一路天真的笑声。我紧紧地追赶着她,任凭树枝抽打着我的脸颊,灌木丛刮破我的衣衫,可我无论如何也追不上她。笑声渐渐远去了,树林里重又恢复了沉寂。久已不见、温存的泪水,涌上了我那干枯的双眼。我哭了。我以为那不过是梦,可是等我醒来,我的枕头却真的湿了一大片,我再也睡不着了。我在想,我曾有过许多虚妄的梦,但我为什么永远没有满足的时候呢?我想追求的究竟又是什么呢!
⑪我忽然醒悟:我最想留住的,还是那永远没有长大、永远没有变老的心啊!只有它,才使我的心里永远充满了诚挚和热爱!只有它,才使我从一次又一次的失望里,不止一千次地得到重生!

Everyone has a birthday. These children live in different parts of the world. They celebrate (庆祝) their birthdays in different ways. For all of them, birthdays are fun!
|
Mark |
Chen |
|
Mark lives in the US. He celebrates his ninth birthday with his friends and family. They sing “Happy Birthday” to him while he blows out the nine candles on his birthday cake. | Chen lives in Hong Kong. Every year at Chen's birthday dinner, his mother serves a bowl (碗) of long noodles. Everyone wishes him a long life, just like noodles. |
| Carmen | Luis |
| Carmen lives in Mexico. She and her friends celebrate her birthday with a pinata. They try to open the pinata so that the candy and the gifts (礼物) will fall out. This birthday celebration is fun for everyone! | Luis lives in Argentina. He is nine years old today. At his birthday party, his brother will gently pull (揪) on his ear nine times. Children get one pull for each year. |
的水解方程式:CO
+2H2O
H2CO3+2OH-
B . 钢铁发生吸氧腐蚀时,负极的电极反应式:Fe-3e-=Fe3+
C . 给锌片上镀铜时,阳极的电极反应式:Zn-2e-=Zn²+
D . 已知中和热为57.3kJ·mol-1 , 稀硫酸与氢氧化钠稀溶液反应的热化学方程式:H2SO4(aq)+2NaOH(aq)=Na2SO4(aq)+2H2O(l) △H=-114.6kJ·mol-1
Subject: Mobile phone problem
Dear Editor,
I am a middle school student. I used to bring a mobile phone with me during school hours. But the teachers think using mobile phone is distraction (分散注意力的事) to students during school hours and also causes so much trouble in class. So now we aren't allowed to bring mobile phones to school.
I find it really inconvenient (不方便的)。 My parents feel unhappy because they can't get in touch with me(不能与我有联系) . But I can't make our school change this rule. What do you think I should do to solve this problem?
Liu Fengyi
Liu fengyi's occupation (职业) | |
Purpose (目的) for writing the e-mail | |
The school rule | Students aren't allowed to |
Thing that Liu Fengyi used to do | She used to |
Reason(原因) why Liu Fengyi's parents are unhappy | They can't |
,在映射f下的对应元素为
,则它原来的元素为( )
B .
C .
D .
是关于
的方程
的两个根,且
.
,
,求
的范围;
.记
,若存在
,使不等式
在其定义域范围内恒成立,求
的取值范围.
;②
;③
;④
,其中正确的是( )
①山西大同一男子因不配合疫情防控检查被行政拘留
②黄某因高空抛物造成行人重伤被起诉支付相应赔偿款
③重庆中级人民法院依法对黑社会组织者王平执行死刑
④香港警方查获190支改装气枪及斧头利刃并拘捕10人
为等差数列
的前n项和.已知
,则( )
B .
C .
D .