组合句子:a good choice ,for,teahouse,going to,like,tea or coffee

A是排列,有顺序的.C是组合,在元素中任取.

(1) C(m,n)=A(m,n)/n!=m!/n!/(m-n)!
(2) C(m,0)=C(m,m)=1
(3) C(m,n)=C(m,m-n)
(4) C(m,n)+C(m,n-1)=C(m+1,n)
(5) C(m,0)+C(m,1)+……+C(m,m)=2^m

组合恒等式Cm/n+C(m+1)/n=C(m+1)/(m+1)这一定要记住
C0/3+C1/4+.+C17/20
=C3/3+C3/4+C3/5+.C3/20
=C4/4+C3/4+C3/5+.C3/20
=C4/5+C3/5+.C3/20
...
=C4/21=5985

(64*63*62*61*60*59*58*57*56*55*54)/(11*10*9*8*7*6*5*4*3*2*1)组

nana

ee ea oa ou ie

C(3,3)+C(3,4)+C(3,5)+C(3,6)+C(3,7)+C(3,8)
=C(4,4)+C(3,4)+C(3,5)+C(3,6)+C(3,7)+C(3,8)
=C(4,5)+C(3,5)+C(3,6)+C(3,7)+C(3,8)
同理=c(4,9)=126
C(94,96)+C(95,97)+C(2,98)+C(2,99)
=c(2,96)+c(2,97）+c（2,98）+c(2,99)
=c(2,2)+c(2,3)+……+c（2,95）+c(2,96)+c(2,97）+c（2,98）+c(2,99)-【c(2,2)+c(2,3)+……+c（2,95）】
=c（3,100）-c（3,96）
=18820
两题的类型是一样的,都是利用了c（m,n）+c(m+1,n)=c(m+1,n+1)这个式子.
上式,老师上课时应该讲过,证明也很简单,用组合数的普式可以证出.

find

Where did you go yesterday?

将6本不同的书平均分给三个人,属于分配问题.是C62*C42*C22,

先考虑甲乙都不在两端的情况
aCb表示组合数从b选出a个
2C3 *2*3*2*1=36
而五人排列总数为5!＝120
所以120-36＝84

exciting
兴奋地
有不会的再问,如果对你有所帮助,请记得及时采纳哦

safe

组合成：busy.意思是 忙碌的、繁忙的、热闹的.

house 房子

pencil

You can help me with my English.

oom房间
doll 玩偶
table 桌子

1/where
2/minute
3/asleep
4/hospital
5/left
6/start
7/straight
8/want
9/north

［(-8)+(+2)］×(-4)×(+1)=24

I think his mother is a docto

moth蛾;蠹,蛀虫

B

3个加号...

your story-book is purple 你的故事书是次藻华丽的/华而不实的.

热爱生命 珍惜生命 宝贵生命

我不太清楚这个题目到底什么意思,还有就是这些字母是怎么排列的,我可以写几个单词：
coffee、no、front、body、about、where

kind 善良的

General Motors is one of the most famous car manufacturers in the car industry around the world

You tell me where is my watch?
你告诉我我的手表在哪里?

the dictinory is under the table

http://www.***.com/English/zkyy/ 自考英语词汇
http://www.***.com/English/cet46tingli/ 英语四级词汇
http://www.***.com/English/kouyitingli/ 口译考试词汇
http://www.***.com/English/ggyytingli/ 公共英...

theirs lunch

CALCULUS这个词共有5种字母,分别是CALUS
然后三个字母进行排列的可能就是5*5*5=125种（可以排相同的字母）
如果不可以重复,则有A5 3=5*4*3=60种

leak泄漏
lake湖

housework家务事 doorbell门铃 upstairs楼上 underline下划线 playground操场 shorthand速记

(8+11-9-10)*(12+13+14)=0.

要看你和他注册的 “类别（小类别）”是不是一样.
相同的话,就不可以.
建议单独注册“鱼堡”,这样是可以的.

doll 洋娃娃

元音音标表（20个）
5个元音的字母音 a [ei] e [i:] i [ai] o [əu] u [u:]
5个元音的短元音：
a [əe] bag cat hat map
e [e] pen bed ten hen
I [i] big pig sit hill
o [כ] box hot dog frog
u [u] but mum bus mug
12个单元音：
短元音[əe] [e] [i] [כ] [۸] [u] [ə]
长元音 [i:] [כ:] [a:] [u:] [ə:]
8个双元音：[ei] [ai] [əu] [au] [כi] [iə] [eə] [uə]
元音发音规则表：
1.单元音/i:/ see me be she need read meal eat seat deep keep
开音节中的e/i:/ me be she
ee /i:/ see sleep deep feet need
ea /i:/ read eat meal seat
2.单元音 /i/ in it is fit pin bit kiss sick miss fish rich lid
闭音节中的i /i/ if,his,film(闭音节指以辅音结尾的音节)
闭音节中的y /i/ sympathy,syllable,system,gym
位于词尾的y /i/ city,pity,willingly,possibility
3.单元音 /e/ get let bed pen best rest wet never better best
闭音节中的e /e/ bed,peg,set,tell
ea /e/ dead,heaven,feather
4.单元音/əe/ hat cat rat cap map fat man thank stamp fact
闭音节中的 a / əe / bad,lad,rat,cab
5.单元音 /a:/ heart arm darn farm cart fast car dark barn pass
ar /a:/ arm,ark,lard,dark,car,card,hard,harm
6.单元音 / כ / lot got job shop soft song top hot box pot lock
闭音节中的o / כ / hot,got,not,lost,on,soft
7./ כ:/ tall fall wall Paul Maud walk call yawn thought
or / כ:/ or,sport,bored,horse,more,before
a(+ll或lk) / כ:/ all,fall,talk,walk
aw / כ:/ law,paw,draw,flaw,claw
8.单元音 /u/ cook book look put good full foot would
u /u/ put,full,pull,push,sugar,cushion
oo /u/ good,took,wood,wool,stood,bedroom
ou /u/ could,would,should
9.单元音 /u:/ too soon rule boot fool school soup cool lose new
oo /u:/ fool,booth,room,food
ou /u:/ soup,you,group
o /u:/ do,to,who
10./ ۸/ cup bus gun hut sung duck lung luck cut stuck
闭音节中的u /۸/ but,hunt,sun,duck,luck
闭音节中的o /۸/ son,once,colour,other,money
ou /۸/ rough,enough,touch,cousin,young
11.单元音 /ə:/ shirt hunt burn girl bird nurse work worm curse
er /ə:/ herd,verb,mercy
ir /ə:/ thirty,shirt,third,fir
ur /ə:/ turn,church,burn,nurse,curse
or /ə:/ word,work,world,worse
ear /ə:/ heard,earth,search
12.单元音 /ə/ ago about asleep above again among mother brother
许多元音在非重读章节中读成/ə/,所以/ə/的拼写形式多种多样.如：
about,sofa,doctor,colour,figure
13.双元音 /ei/ May pay way day same hay great gain pain spade
a /ei/ save,face,pale
ay /ei/ day,pay,may
ai /ei/ wait,fail,strait
ea /ei/ break,great
14.双元音 /əu/ no go so hole hope road home slow load foe soul
o /əu/ go,hello,no,open,over,joking,October
oa /əu/ coat,soap,boat,road,coast
ow /əu/ snow,throw,blow,show,know,window
15.双元音 /ai/ bye lie try eye cry die my five time mine like
开音节中的i /ai/ time,crime,rite,fine
igh /ai/ high,might,night,light,bright
y /ai/ cry,my,sky,fly,July,reply
ie /ai/ eye,dye,bye
16.双元音 /au/ how now cow out mouse down house brown found
ou /au/ about,around,found,sound,mouse
ow /au/ down,crowd,town,brown,now,how
17.双元音 /כi/ boy joy toy voice noise join coin oil soil toil
oi /כi/ oil,boil,join,coin,spoilt,voice,choice,noise
oy /כi/ toy,boy,enjoy,destroy,annoy,loyal,employer
18.双元音 /iə/ ear here fear hear dear pier tear near really idea
ear /iə/ ear,dear,hear,clear,beard
ea /iə/ idea,real,theatre
ere /iə/ here,mere,severe
eer /iə/ beer,queer,engineer
19.双元音 /eə/ care wear hair there fair careful various
are /eə/ care,share,fare,hare,careless
air /eə/ air,fair,chair,repair
20.双元音 /uə/ tour sure poor pure cure tourist
ur /uə/ cure,pure,fury

98765+1234=99999

weather 天气

C(a,b)=a!/(b!*(a-b)!)
P(a,b)=a!/b!

luggage = 行李