若複數2-bi/1+2i的實部與虛部互為相反數，求出b的值

若複數2-bi/1+2i的實部與虛部互為相反數，求出b的值

即（2-bi）（1-2i）的實部和虛部互為相反數，展開
Re=2-2b
Im=-b-4
故2-2b=b+4，b=-2/3
複數5/1+i^3化成a+bi的形式，注意那個是一加字母i的三次，沒有看清不要回答，
=5/（1+3*i+3*i²；+i³；）
=5/（1+3i-3-i）
=5/（-2+2i）
=5（-2-2i）/（-2+2i）（-2-2i）
=5（-2-2i）/（4+4）
=-5/4-（5/4）i
i^2=-1
i^3=-i
5/（1+i^3）=5/（1-i）=5（1+i）/（1+1）=5/2+5/2i
a=5/2 b=5/2
英語“look”的名詞，動詞用法，以及短語
have a good look at好好看看……
look around四下張望
look ahead向前看
look back回頭看、回顧
look right/left向右看/左看
look well看起來健康
look ill看上去有病
in good looks氣色好
look down on（upon）看不起、經視
look over檢查
look like看起來像
look out向外望、當心
look up向上看、查（字典）
look down往下看
look up and down上下打量
look into往裏看
look for尋找
look after照看、照顧
1）環顧四周.如：
The man kept looking about.這個人不停地環顧四周.
（2）隨便看，到處看.如：
A:What can I do for you，madam？夫人，想買什麼嗎？
B:No，I’m just looking around.不是，只是隨便看看.
（3）到處尋找.如：
I’m looking about for a house.我在找一座房子.
（4）仔細考慮.如：
Look about carefully before making the decision.先仔細考慮，然後再作决定.
2. look after照顧，照料，關心.如：
I can look after myself.我能照顧自己.
Who is looking after the luggage？誰在照看行李？
3. look at
（1）看……，注視…….如：
He looked at me and smiled.他望著我笑了.
Look at him jump [jumping].請看他跳.
（2）看待.如：
That’s the way I look at it.我就是那樣看待它的.
（3）考慮（多用於含有否定意義的句子）.如：
They refused to look at my suggestion.他們拒不考慮我的建議.
（4）檢查.如：
He came to look at the drainage.他是來檢查排水設備的.
4. look back
（1）回顧，回想.如：
I still shudder when I look back on the past.想起過去，我仍然不寒而慄.
（2）停滯，畏縮，倒退（通常用於否定句）.如：
From this time on，he never looked back.從此以後，他便不斷進步.
5. look down on [upon]看不起，瞧不起.如：
You shouldn’t look down upon the poor.你不應該瞧不起窮人.
She likes tennis，but looks down on football.她喜歡網球，但輕視足球.
6. look for
（1）尋找.如：
I’ve looked for it everywhere.我到處找過它了.
You are looking for trouble.你是在自找麻煩
（2）期待，指望.如：
We shall be looking for an improvement in your work this term.我們期待你這學期學習進步.
It’s too soon yet to look for results.現在就指望有結果，未免為時過早.
7. look forward to期待，盼望.如：
We’re looking forward to hearing from you.我們盼望收到你的來信.
The children are looking forward to your visit.孩子們都盼望著你的到來.
注：該結構中的to是介詞，不是不定式符號，所以其後接動詞時要用動名詞，而不用動詞原形.
8. look in（順便）來訪.如：
Why don’t you look in（on）me next time you’re in town？你下次進城來順便來串串門好嗎？
I may look in at the party on my way home.我回家時可能順便到聚會處去看看.
9. look into調查，研究，瞭解.如：
We’ll look into that right away.我們會馬上調查此事.
The police are looking into the cause of the accident.警方正調查事故原因.
10. look like
（1）看起來象.如：
He looks like your brother.他看上去象你哥哥.
What does he look like？他長相如何？
He looks like an honest man.看來他象個老實人.
（2）好象要，似乎要.如：
It looks like rain [raining].好象要下雨了.
He looks like winning.好象他要贏了.
11. look on
（1）旁觀.如：
No，I’m not playing；I’m just looking on.不，我不打，我只是看看.
（2）看（待）（尤指帶有某種目光或情緒等）.如：
She was looked on with distrust.人家對她總是不信任.
（3）看作，當作（與as連用）.如：
He looks on me as his best friend.他把我當作最好的朋友.
We looked on this as useless.我們認為這個東西毫無用處.
12. look out
（1）向外看.如：
Don’t look out of the window.別往窗外看.
He stood at the window and looked out（at the view）.他站在窗前向外望（觀看景色）.
（2）注意，當心，小心.如：
Look out. There’s a car coming！當心！汽車來了！
If you don’t look out，you’ll hurt yourself.你若不當心，你會受傷的.
（3）找出，挑選出.如：
We looked out his address in，the telephone directory.我們在電話簿裏查到了他的地址.
13. look over審閱，翻閱，打量，檢查.如：
Would you mind looking over my exercises？請你幫我看一下我的練習好嗎？
He looked her over and nodded lightly.他上下打量她，然後微微點了點頭.（
14. look through翻閱，瀏覽.如：
Before the meeting he looked through the reports.開會前他把報告看了一遍.
Look through your notes before the examination.考試前翻翻你的筆記.
15. look to注意，負責.如：
The country must look to its defences.這個國家必須加强防務.
Look to it that this doesn’t happen again.注意不要讓這事再發生.
16. look up
（1）查閱，查找.如：
Look up this word in the dictionary.這個詞查查詞典吧.
（2）看望，拜訪，找（人）.如：
I want to look up an old friend.我想去看一比特朋友.
（3）好轉.如：
Things are looking up.情况在好轉
17. look up to尊敬.如：
I look up to my parents.我尊敬父母.
He is good teacher. We’ve always look up to him.他是比特好老師，我們一向尊重他.
及物動詞vt. &不及物動詞vi.
* 1.看，瞧
Look whether the postman has been yet.
去看看郵差來過沒有。
不及物動詞vi.
* 1.面向，朝向
The house looks south.
這棟房子面朝南。
…展開
及物動詞vt. &不及物動詞vi.
* 1.看，瞧
Look whether the postman has been yet.
去看看郵差來過沒有。
不及物動詞vi.
* 1.面向，朝向
The house looks south.
這棟房子面朝南。
The offices look onto a park.
這幾家辦公室面對著公園。
* 2.尋找；尋求
* 3.注意；留心；留神
* 4.與…外表相似；好像；仿佛
* 5.看起來好像；似乎有可能
* 6.面向；正對；朝向
系動詞link-v.
* 1.看來，顯得
He looks an honest man.
看來他像個誠實的人。
He's beginning to look his age.
他看上去和他的年齡相稱。
She looks much younger than she is.
她看起來比她實際年齡要年輕得多。
She was looking her best.
她那時顯得很美。
He looked blank when he was informed of his dismissal.
當被告知自己被解雇時，他顯得茫然。
It looks very suspicious to me.
我覺得這事似乎很不可靠。
They looked as if they didn't care.
他們看起來好像不在乎。
It looks as if it were going to rain.
天好像要下雨了。
It looks as if we were going to have fine weather.
天好像要放晴了。
It looks as if there will be a strike.
看來將有一場罷工運動。
It looks as if the coming autumn harvest will be even better than the last one.
看來即將到來的秋收會比去年更好。
* 2.看起來好像，似乎，顯得
名詞n.
* 1.看，瞥
I took a close look at her photo.
我仔細地看了一下她的照片。
* 2.眼神；表情；神情；神色；臉色
She assumed a look of innocence.
她裝出一副天真無邪的樣子。
* 3.（尤指吸引人的）相貌，容貌，美貌
She used her good looks to compensate her lack of intelligence.
她利用她漂亮的外表來彌補智力的不足。
* 4.查找
* 5.樣子；外觀；相貌；外表
* 6.時尚；式樣；風格
感歎詞interj.
* 1.（插話或喚起注意）喂，聽我說收起
vt. & vi.
看，瞧
Look whether the postman has been yet.
去看看郵差來過沒有。
vi.
面向，朝向
The house looks south.
這棟房子面朝南。
The offices look onto a park.
這幾家辦公室面對…展開
vt. & vi.
看，瞧
Look whether the postman has been yet.
去看看郵差來過沒有。
vi.
面向，朝向
The house looks south.
這棟房子面朝南。
The offices look onto a park.
這幾家辦公室面對著公園。
link v.
看來，顯得
He looks an honest man.
看來他像個誠實的人。
He's beginning to look his age.
他看上去和他的年齡相稱。
She looks much younger than she is.
她看起來比她實際年齡要年輕得多。
She was looking her best.
她那時顯得很美。
He looked blank when he was informed of his dismissal.
當被告知自己被解雇時，他顯得茫然。
It looks very suspicious to me.
我覺得這事似乎很不可靠。
They looked as if they didn't care.
他們看起來好像不在乎。
It looks as if it were going to rain.
天好像要下雨了。
It looks as if we were going to have fine weather.
天好像要放晴了。
It looks as if there will be a strike.
看來將有一場罷工運動。
It looks as if the coming autumn harvest will be even better than the last one.
看來即將到來的秋收會比去年更好。
n.
看，瞥
I took a close look at her photo.
我仔細地看了一下她的照片。
臉色，神色，表情
She assumed a look of innocence.
她裝出一副天真無邪的樣子。
美貌
She used her good looks to compensate her lack of intelligence.
她利用她漂亮的外表來彌補智力的不足。收起
What did it get so out of hand？
out of hand無法控制
為什麼它變得如此不受控制？野了，hoho~