Đa thức $2x^4-21x^2+1$ không phân tích thành nhân tử bạn nhé.

1 to know

2 to meet

3 will tell

4 has just gone

5 has already known

6 to do

7 read

8 has just left

9 learn

#\(yGLinh\)

1. They ought ( know ) ..to know.. all the regulations in this school

2. It's very happy ( meet ) ..to meet. them again

3.I am sure they ( tell ) ..will tell. us about themselves soon

4. Nam isn't here. He ( just go ) .has just gone.. out for a walk

5. He (already know ) ..has already known. this regulation

6. Of us is ready ( do ) ..to do. the work

7. Have you ever ( read ) ...read. the story

8. Our teacher ( just leave ) ..has just left. the school

9. Pupils must ( learn) ..learn. their lessons before coming to class

Dưới đây là các câu hoàn chỉnh với các từ đã cho:

1. All of them have ready to give a book report. -> All of them are ready to give a book report.

2. We are much interested in English. -> We are very much interested in English.

3. Ask when he made the cake. -> Ask him when he made the cake.

4. Jane has never seen an elephant before. -> Jane has never seen an elephant before.

5. Enjoy books in spare time. -> I enjoy reading books in my spare time.

/s/: stops, arts, laughs, rocks

/iz/: quizzes, fixes, watches

/z/: friends, prefers

/ɪz/: quizzes, fixes, watches

/s/: stops, arts, laughs, rocks

/z/: friends, prefers

1. To learn the regulations is difficult

=> it is...difficult to learn the regulations.

2. To pratise swimming is good for your health

=> it is good for your health to practice swimming.

3. To help him write his name on the board was necessary

=> it was...necessary to help him write his name on the board.

4. To get acquainted with newcomers is easy

=> it is not... difficult to get acquainted with newcomers.

1. To learn the regulations is difficult

=> it is...difficult to learn the regulations

2. To pratise swimming is good for your health

=> it is good for your health to practise swimming

3. To help him write his name on the board was necessary

=> it was...necessary to help him write his name on the board 

4. To get acquainted with newcomers is easy

=> it is not... difficult to get acquainted with newcomers

1. Do you agree .with.. me .on..this problem?

2. Making friends is easy .for.. him

3. Let's listen ..to. what he says

4. I cannot help you now because i am ..in. a hurry

5. What are you afraid .of..?

6. The street is crowded .with.. people

7. He was born .on.. June 15th , 1987

8. I intend to buy something .for.. my mother

9. Tom often takes a bus .to.. his school

1 with - on

2 to

3 to

4 in

5 of

6 with

7 on

8 for

9 to

#\(yGLinh\)

\(n_{co_2}=\dfrac{0,896}{22,4}=0,02\left(mol\right)\)

\(n_{BaCl_2}=\dfrac{100.20,8\%}{208}=0,1\left(mol\right)\)

PTHH : 

\(BaCl_2+Na_2CO_3\rightarrow BaCO_3+2NaCl\) (1)

Như vậy : dung dịch X gồm \(BaCO_3;NaCl;\) có thể có \(BaCl_2\) dư hoặc \(Na_2CO_3\) dư

PTHH : 

\(BaCO_3+H_2SO_4\rightarrow BaSO_4+CO_2+H_2O\) (2)

ctc : \(Na_2CO_3+H_2SO_4\rightarrow Na_2SO_4+CO_2+H_2O\) (3)

+) TH1 : Nếu \(BaCl_2\) dư ( không có phản ứng (3) )

Theo phương trình (2) \(\Rightarrow n_{BaCO_3}=n_{CO_2}=0,04\left(mol\right)\)

Theo phương trình (1) \(\Rightarrow n_{Na_2CO_3}=n_{BaCO_3}=0,04\left(mol\right)\)

\(\Rightarrow m_{Na_2CO_3}=0,04.106=4,24\left(g\right)\)

\(\Rightarrow C_{\%ddNa_2CO_3}=\dfrac{4,24.100\%}{100}=4,24\%\)

BTKL \(\Rightarrow m_{ddBaCl_2}+m_{ddNa_2CO_3}+m_{ddH_2SO_4}=m_{ddspứ}+m_{CO_2}\)

\(\Rightarrow m_{ddBaCl_2}+m_{ddNa_2CO_3}+m_{ddH_2SO_4}-m_{CO_2}=m_{ddspứ}\)

\(\Rightarrow m_{ddspứ}=100+100+100-0,04.44=298,14\left(g\right)\)

+) TH2 : Nếu \(Na_2CO_3\) dư ( xảy ra phản ứng (3) )

Theo phương trình (1) \(\Rightarrow n_{BaCO_3}=n_{BaCl_2}=0,1\left(mol\right)\)

Theo phương trình (2) \(\Rightarrow n_{CO_2\left(2\right)}=n_{BaCO_3\left(1\right)}=0,1\left(mol\right)>0,04\left(mol\right)\) ( vô lí ) 

\(\Rightarrow\) TH2 loại

1 of

2 in- to 

3 with

4 with

5 with

6 with

#\(yGLinh\)

1. What are you fond ..of.

2.The schoolboys and schoolgirls gathered .in.. small groups and talked .to.. one another

3. It is difficcult to get acquainted ..with. newcomers

4. My from teacher is rather strict ..with. us

5. They look at their new school .with.. curious eyes

6. The pupils were busy ..with. their work

Sửa đề: Kẻ đường thẳng vuông góc với NP tại P và đường thẳng vuông góc với MQ tại Q, hai đường thẳng này cắt nhau tại E

Gọi K là giao điểm của MQ và NP

Xét ΔKQE vuông tại Q và ΔKPE vuông tại P có

KE chung

EQ=EP

Do đó: ΔKQE=ΔKPE

=>KQ=KP

=>ΔKQP cân tại K

=>\(\hat{KQP}=\hat{KPQ}\)

=>\(\hat{MQP}=\hat{NPQ}\)

Hình thang MNPQ có \(\hat{MQP}=\hat{NPQ}\)

nên MNPQ là hình thang cân