-(3/1a)=2,a=?说错了，是-(-3/1a)=2，a=？

路人以目

我跟你有同样的困惑.
我自己的解决方案：1、少说话；2、说话之前慢慢想好,不要着急着把话讲出来；3、在可以的情况下,不知道该怎么讲话时就不讲.

My English is not really good,I'm just a beginner to learn English,if I made any mistakes please don't laugh at me,hope you can correct it,I'll appreciate you.

你可能搞错了,平方分米是面积单位,毫升是体积单位
1立方分米=1000立方厘米=1升=1000毫升

脱口而出的有那么纠结呀

Exhibition of Egyptian Cultural Relics

设在椭圆上有一点P（x1,y1)经过此点椭圆的切线方程为：x1*x/a^2+y1*y/b^2=1
方法一：设切线的方程为Y-Yo=k(X-Xo)即Y=k(X-Xo)+Yo ①
把①式代入椭圆方程X^2/a^2+Y^2/b^2=1,得：
X^2/a^2+[k(X-Xo)+Yo]^2/b^2=1即：
b^2·X^2+a^2·[k^2·(X-Xo)^2+Yo^2+2Yo·k(X-Xo)]=a^2·b^2即：
(b^2+a^2·k^2)X^2-(2a^2·k^2·Xo-2a^2·k)X+(a^2·k^2·Xo^2+a^2·Yo^2-2a^2·k·Xo-a^2·b^2)=0
由于切线Y-Yo=k(X-Xo)与椭圆X^2/a^2+Y^2/b^2=1相切,所以上式方程有且只有一个实数解.
则△=(2a^2·k^2·Xo-2a^2·k)^2-4(b^2+a^2·k^2)(a^2·k^2·Xo^2+a^2·Yo^2-2a^2·k·Xo-a^2·b^2)=0
则有k=-(b^2·Xo)/(a^2·Yo)
把k=-(b^2·Xo)/(a^2·Yo)代入切线方程Y-Yo=k(X-Xo),得：
(a^2·Yo)(Y-Yo)=-(b^2·Xo)(X-Xo)即：
a^2·Yo·Y+b^2·Xo·X=a^2·Yo^2+b^2·Xo^2 ②
又把点(Xo,Yo)代入椭圆方程X^2/a^2+Y^2/b^2=1,得：
Xo^2/a^2+Yo^2/b^2=1 即 b^2·Xo^2+a^2·Yo^2=a^2·b^2 ③
把③式代入②式,得：
a^2·Yo·Y+b^2·Xo·X=a^2·b^2
等式两边同时除以a^2·b^2,得：
Xo·X/a^2 + Yo·Y/b^2=1
方法二：用隐函数求导
有 椭圆方程两边分别对x求导：
b²x²+a²y²-a²b²=0
2b²x+2a²y*(dy/dx)=0
(dy/dx)=-b²x1/(a²y1)
即k=-b²x1/(a²y1)
则切线方程是：y-y1=k*(x-x1)=[-b²x1/(a²y1)](x-x1)
(y-y1)(a²y1)+b²x1(x-x1)=0
a²yy1+b²x1x-（a²y1²+b²x1²）=a²yy1+b²x1x-a²b²=0
即：xx1/a²+yy1/b²=1
双曲线过点（x0,y0)的切线为
x0*x/(a^2)-y0*y/(b^2)=1
证明：x²/a²-y²/b²=1.对x求导：2x/a²-2yy′/b²=0.
（x0,y0）的切线斜率y′=x0b²/y0a²
（x0,y0）的切线方程：（y-y0）＝x0b²/y0a²（x-x0）.
注意到b²x0²-a²y0²＝a²b².
切线方程k可化简为：x0x／a²-y0y／b²＝1.
求抛物线:y^2=2px 在点(a,b)处切线的方程
抛物线方程两边对x求导:得:
2yy'=2p 即 y'=p/y
故抛物线在(a,b)处切线的斜率为p/b
所以在(a,b)处切线方程为:y-b=（p/b）(x-a)
又:b^2=2pa 所以 y+b=p(x+a)
即抛物线y^2=2px在(a,b)处切线方程为:y+b=p(x+a)

嗯,差不多是这样.
不过可逆循环的环境并不是一个物体,而是要分为高温热源和低温热源两个物体.

肯定是2*10的-3次方,只要数小数点后有几位数字就是负几次方

陶器和瓷器的主要区别如下：1.陶器未玻化或玻化程度不高,结构不致密,断面粗糙；而瓷器玻化程度高,结构致密,细腻,断面呈石状或背壳状；2.陶器不透光,而瓷器透光；3.陶器敲击声沉浊,而瓷器声音清脆弱；4.陶器的吸水率一般大于3%,而瓷器在3%以下.

Dog has four legs and feet
狗有四条腿

twelve o'clock

工业制Al的原料：氧化铝
不电解熔融AlCl₃炼Al 原因：AlCl₃是共价化合物,其熔融态不导电

因为 正方体中D1C1垂直平面BCC1B1 B1C垂直BC1 所以BD1垂直B1C （三垂线定理）

你刚才说错了,把铅笔说成了钢笔
You just wrong,that became pen pencil
你刚才说错了,把铅笔说成了钢笔.
You just wrong,said his pencil into the pen.

幽 山 幽静的意思
醉 酉 沉醉
炼 火 锻炼

建议上一些英语论坛,里面很多材料
比如特普

这道题是对的.你老爸错了.大于等于符号表示有两种可能是成立的,其中只要有一种是对的,这道题就对了.1永远都大于等于1!

动词有生（小孩）的意思,过去时是born,过去分词是borne

化学能转化为内能
C+O2=CO2(点燃)
2Mg+O2=2MgO（点燃）
CH4+2O2=CO2+2H2O（点燃）
CaO+H2O=Ca(OH)2
化学能转化为电能
原电池
锌片：Zn - 2e- = Zn2+ (氧化反应）
铜片：2H+ + 2e- = H2↑ （还原反应）
总反应：Zn＋2H+ = Zn2+ + H2↑
电能转化成化学能
2NaCl+2H2O=2NaOH+H2↑+Cl2↑（通电）

科学家们推测,在3月底会有一股冷空气侵袭北京.

过二点只有一条直线!
线段和直线不是一个概念,线段可以有无数种长短,就算是过二点也是一样,就比如过距离为二厘米的两点,直线只有一条,线段的话,只要大于或等于二厘米就行.

Infinitive (涓嶅畾璇?Past tense (杩囧幓寮?Past Participle (杩囧幓鍒嗚瘝)
abide abode,abided abode,abided
arise arose arisen
awake awoke awaked,awoken
be was been
bear bore borne,born
beat beat beaten
become became become
befall befell befallen
beget begot begotten
begin began begun
behold beheld beheld
bend bent bent
bereave bereaved,bereft bereaved,bereft
beseech besought besought
beset beset beset
bet bet,betted bet,betted
betake betook betaken
bethink bethought bethought
bid bade,bid bidden,bid
bind bound bound
bite bit bitten,bit
bleed bled bled
blend blended,blent blended,blent
bless blessed,blest blessed,blest
blow blew blown
break broke broken
breed bred bred
bring brought brought
broadcast broadcast,broadcasted broadcast,broadcasted
build built built
burn burnt,burned burnt,burned
burst burst burst
buy bought bought
cast cast cast
catch caught caught
chide chided,chid chided,chidden
choose chose chosen
cleave clove,cleft cloven,cleft
cling clung clung
clothe clothed,clad clothed,clad
come came come
cost cost cost
creep crept crept
crow crowed,crew crowed
cut cut cut
dare dared,durst dared
deal dealt dealt
dig dug dug
dive dived,(US)dove dived
do did done
draw drew drawn
dream dreamt,dreamed dreamt,dreamed
drink drank drunk
drive drove driven
dwell dwelt dwelt
eat ate eaten
fall fell fallen
feed fed fed
feel felt felt
fight fought fought
find found found
flee fled fled
fling flung flung
fly flew flown
forbear forbore forborne
forbid forbade,forbad forbidden
forecast forecast,forecasted forecast,forecasted
foreknow foreknew foreknown
foresee foresaw foreseen
foretell foretold foretold
forget forgot forgotten
forgive forgave forgiven
forsake forsook forsaken
forswear forswore forsworn
freeze froze frozen
gainsay gainsaid gainsaid
get got got,(US)gotten
gild gilded,gilt gilded
gird girded,girt girded,girt
give gave given
go went gone
grave graved graven,graved
grind ground ground
grow grew grown
hamstring hamstringed,hamstrung hamstringed,hamstrung
hang hung,hanged hung,hanged
have had had
hear heard heard
heave heaved,hove hesved,hove
hew hewed hewed,hewn
hide hid hidden
hit hit hit
hold held held
hurt hurt hurt
inlay inlaid intaid
keep kept kept
kneel knelt knelt
knit knitted,knit knitted,knit
know knew known
lade laded laden
lay laid laid
lead led led
lean leant,leaned leant,leaned
leap leapt,leaped leapt,leaped
learn learnt,learned learnt,learned
leave left left
lend lent lent
let let let
lie lay lain
light lit,lighted lit,lighted
lose lost lost
make made made
mean meant meant
meet met met
melt melted melted,molten
miscast miscast miscast
misdeal misdealt misdealt
misgive misgave misgiven
mislay mislaid mislaid
mislead misled misled
misspell misspelt misspelt
misspend misspent misspent
mistake mistook mistaken
misunderstand misunderstood misunderstood
mow mowed mown,(US) mowed
outbid outbid outbid
outdo outdid outdone
outgo outwent outgone
outgrow outgrew outgrown
outride outrode outridden
outrun outran outrun
outshine outshone outshone
overbear overbore overborne
overcast overcast overcast
overcome overcame overcome
overdo overdid overdone
overhang overhung overhung
overhear overheard overheard
overlay overlaid overlaid
overleap overleapt,overleaped overleapt,overleaped
overlie overlay overlain
override overrode overridden
overrun overran overun
oversee oversaw overseen
overshoot overshot overshot
oversleep overslept overslept
overtake overtook overtaken
overthrow overthrew overthrown
partake partook partaken
pay paid paid
prove proved proved,proven
put put put
quit quitted,quit quitted,quit
read read[red] read[red]
rebind rebound rebound
rebuild rebuilt rebuilt
recast recast recast
redo redid redone
relay relaid relaid
remake remade remade
rend rent rent
repay repaid repaid
rerun reran rerun
reset reset reset
retell retold retold
rewrite rewrote rewritten
rid red,redded rid,ridded
ride rode ridden
ring rang rung
rise rose risen
rive rived riven,rived
run ran run
saw sawed sawn,sawed
say said said
see saw seen
seek sought sought
sell sold sold
send sent sent
set set set
sew sewed sewn,sewed
shake shook shaken
shave shaved shaved,shaven
shear sheared sheared,shorn
shed shed shed
shine shone shone
shoe shod shod
shoot shot shot
show showed shown,showed
shrink shrank,shrunk shrunk,shrunken
shrive shrove,shrived shriven,shrived
shut shut shut
sing sang,sung sung
sink sank,sunk sunk,sunken
sit sat sat
slay slew slain
sleep slept slept
slide slid slid
sling slung slung
slink slunk slunk
slit slit slit
smell smelt,smelled smelt,smelled
smite smote smitten
sow sowed sown,sowed
speak spoke spoken
speed sped,speeded sped,speeded
spell spelt,spelled spelt,spelled
spend spent spent
spill spilt,spilled spilt,spilled
spin spun,span spun
spit spat,spit spat,spit
spoil spoilt,spoiled spoilt,spoiled
spread spread spread
spring sprang,sprung sprung
stand stood stood
stave staved,stove staved,stove
steal stole stolen
stick stuck stuck
sting stung stung
stink stank,stunk stunk
strew strewed strewn,strewed
stride strode stridden,strid
strike struck struck,stricken
string strung strung
strive strove striven
swear swore sworn
sweep swept swept
swell swelled swollen,swelled
swim swam swum
swing swung swung
take took taken
teach taught taught
tear tore torn
tell told told
think thought thought
thrive throve,thrived thriven,thrived
throw threw thrown
thrust thrust thrust
tread trod trodden,trod
unbend unbent unbent
unbind unbound unbound
underbid underbid underbid,underbidden
undergo underwent undergone
understand understood understood
undertake undertook undertaken
undo undid undone
upset upset upset
wake woke,waked woken,waked
waylay waylaid waylaid
wear wore worn
weave wove woven
weep wept wept
win won won
wind wound wound
withdraw withdrew withdrawn
withhold withheld withheld
withstand withstood withstood
work worked,wrought worked,wrought
wring wrung wrung
write wrote written

You are right/wrong.你说的对/不对.
谈话：You didn't get it.也可以像上面那样说.

1/3.6米每秒,你想说什么

这句话是对的.

The reason why we love and support you is not that you have a extraordinary performance,but we want to strive to achieve the same goal in conjunction with you .
或者是Whether you have a extraordinary performance ,we still love snd support you.
It is our common goal to make you to be the best.
翻译的太奇怪了.

不对.
光解水,产生氧气,而不是光能的转化.
你可以理解成,光起到了化学反应的催化.

固态铁作阳极,和置换反应一样,最多只会被氧化成Fe2+.除非用惰性电极继续氧化,否则不会得到Fe3+.
换个角度想,Fe + 2Fe3+=3Fe2+自发反应,铁电极不能和Fe3+共存,只能生成Fe2+.

CH2=CH2+Cl2→CH2ClCH2Cl
CH2ClCH2Cl+H2O→(碱性条件下)CH2OHCH2OH+2HCl

不是生殖细胞
生殖细胞就是指精子、卵细胞这种染色体只有体细胞一半的遗传物质传递“桥梁”,受精卵实际上是人体的第一个体细胞.

p的充分条件是非p的充分条件的既不充分也不必要条件,也就是说两者的交集是空集

水作为弱电解质,所以发生微弱的电离

平方分米是面积单位 ,升是体积单位 也等于立方分米

多读英文的文章,多听英文原声,每次说的时候都要注意不要说错
坏习惯一旦养成就需要下很大功夫去改正,所以要多说多练,自然而然就改正了
还有以后学英语的时候要注意一些重要的点,在一开始就防止错误,总比以后在下更大的功夫去改要容易得多

No.69 WeiXin Road,Industrial park,Suzhou

棱锥底面是三角形,三角形面积乘以高再乘以3分之1就是棱锥的体积.圆的面积是半径乘半径乘π,圆柱要在乘以高,圆锥要在乘以3分之1.
希望能帮到你.

不管我说不说,万物皆存在（这是哲学上的）
首先A B将圆分成两半,一般来说弧AB是指较短的那条弧（这样比较方便而已）通常我们也是写较短的弧.AC AC阿!写错了.我是存在的!哈哈

是或的意思

因为 a>0, b 0
所以 原式>0 恒成立
所以 a-(b-a)的绝对值= a-(b-a) = 2a-b
还有,无论a,b谁正谁负,原式拆括号化简的结果都是 2a-b,然后在判断绝对值即可.楼上说 -b 的一个比一个挫.

Na2S不足量：2Fe3+ + S2- = 2Fe2+ + S↓
Na2S过量：2Fe3+ + 3S2- = 2FeS↓ + S↓

12cm-15cm 要看你的假山多大

邗 han

I am not good at English,so please forgive me if there are something wrong in my words

1GB=1024MB 1MB=1024KB
所以1G=1048576KB
1KG=0.00000095367431640625G

笑话是自然而然,必不缺少的,你只要多用点心,多努力,多下功夫,改明儿,就换你嘲笑他们了!加油~我相信你可以的!

不一定
只能说,近地点离地球中心的距离 在[R,2R)范围时,有可能大于第一宇宙
看椭圆的离心率多大
近地点速度=sqrt((1+e)GM/r),第一宇宙=sqrt(GM/R)
两式联立,椭圆离心率 范围 [0,1)
求

很多寄生植物不产生叶绿素,不进行光合作用
根据对寄主的依赖程度不同,寄生性种子植物可分为两类.
半寄生种子植物
一类是半寄生种子植物：有叶绿素,能进行正常的光合作用,但根多退化,导管直接与寄主植物相连,从寄主植物内吸收水分和无机盐.全寄生种子植物
另一类是全寄生种子植物：没有叶片或叶片退化成鳞片状,因而没有足够的叶索,不能进行正常的光合作用导管和筛管与寄主植物相连,从寄主植物内吸收全部或大部养分和水分.例如,菟丝子(Cusutaspp.)和列当(Orobanchespp.)等.根据寄生部位不同,寄生性种子植物还可分为茎寄生和根寄生植物寄生.寄生在植物地上部分的为茎寄生,如菟丝子、桑寄生等；寄生在植物地下部分的为根寄生,如列当等.寄生性种子植物对寄主植物的影响,主要是抑制其生长.草本植物受害后,主要表现为植株矮小、黄化,严重时全株枯死.木本植物受害后,通常出现落叶、落果、顶枝枯死、叶面缩小,开花延迟或不开花,甚至不结实