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AH
Akai Haruma
Giáo viên
16 tháng 12 2023

Lời giải:
Theo đề thì AB là đường trung bình ứng với đáy NP của tam giác $MNQ$.

$\Rightarrow AB=\frac{NP}{2}=\frac{18}{2}=9$ (cm)

AH
Akai Haruma
Giáo viên
16 tháng 12 2023

Cần bổ sung thêm điều kiện về $x$ để tính min bạn nhé. Bạn xem lại đề.

15 tháng 12 2023

A B C M N O

Hai tam giác ACM và tg BCM có chung đường cao từ C->AB nên

\(\dfrac{S_{ACM}}{S_{BCM}}=\dfrac{AM}{BM}=1\Rightarrow S_{ACM}=S_{BCM}=\dfrac{S_{ABC}}{2}=\dfrac{70}{2}=35cm^2\) 

Hai tg BCN và tg ABN có chung đường cao từ B->AC nên

\(\dfrac{S_{BCN}}{S_{ABN}}=\dfrac{CN}{NA}=\dfrac{2}{3}\) mà \(S_{BCN}+S_{ABN}=S_{ABC}=70cm^2\)

\(\Rightarrow S_{BCN}=2x\dfrac{S_{ABC}}{2+3}=2x\dfrac{70}{5}=28cm^2\)

\(\Rightarrow S_{ABN}=S_{ABC}-S_{BCN}=70-28=42cm^2\)

Hai tg AMN và tg BMN có chung đường cao từ N->AB nên

\(\dfrac{S_{AMN}}{S_{BMN}}=\dfrac{AM}{BM}=1\Rightarrow S_{AMN}=S_{BMN}=\dfrac{S_{ABN}}{2}=\dfrac{42}{2}=21cm^2\)

Hai tam giác BMN và tam giác BCN có chung BN nên

\(\dfrac{S_{BMN}}{S_{BCN}}=\) đường cao từ M->BN / đường cao từ C->BN \(=\dfrac{21}{28}=\dfrac{3}{4}\)

Hai tg BOM và tam giác BOC có chung BO nên

\(\dfrac{S_{BOM}}{S_{BOC}}=\) đường cao từ M->BN / đường cao từ C->BN \(=\dfrac{3}{4}\)

Mà \(S_{BOM}+S_{BOC}=S_{BCM}=28cm^2\)

\(\Rightarrow S_{BOC}=4x\dfrac{S_{BCN}}{4+3}=4x\dfrac{28}{7}=16cm^2\)

15 tháng 12 2023

Sorry!

Mà \(S_{BOM}+S_{BOC}=S_{BCM}=35cm^2\)

\(\Rightarrow S_{BOC}=4x\dfrac{S_{BCM}}{4+3}=4x\dfrac{35}{7}=20cm^2\)

A. PHONETICS, VOCABULARY AND GRAMMAR. I. Choose the word whose underlined part is pronounced differently from that of the others. 1. A. switch       B. stomach C. match D. catch 2. A. laughs B. cars C. stops D. works 3 A. chalk B. ship C. machine D. champagne 4 A. honest B....
Đọc tiếp

A. PHONETICS, VOCABULARY AND GRAMMAR.

I. Choose the word whose underlined part is pronounced differently from that of the others.

1.

A. switch      

B. stomach

C. match

D. catch

2.

A. laughs

B. cars

C. stops

D. works

3

A. chalk

B. ship

C. machine

D. champagne

4

A. honest

B. honor        

C. hour

D. homework

5.

A. watched

B. reduced

C. coughed

D. raised

6

A. host

B. cold

C. short

D. close

7

A. sound

B. suggestion

C. island

D. selection

8

A. thirsty

B. guitar

C. dirty

D. listen

9

A. debt          

B. public

C. climber

D. thumb

10

A. effective

B. of

C. deaf

D. favorite

II.  Choose the most suitable word or phrase.

1. The window ____________  last night has been repaired.

A. break

B. broke

C. broken

D. breaking

2. It took him ages to  ____________   living in the new town.

A. get use to

B. will use to

C. will used to

D. be used to

 

3. My parents make me ____________  for my exam.

A. to study

B. study

C. studying   

D. studied

4.  I would rather you  ____________  me the story.

A. tell

B. told

C. to tell

D. telling

5. That’s a  ____________   building.

A. five- floor

B. five- floors

C. five- floor’s

D. five- floors’

6. She helped me ____________  the house..

A. to clean

B. cleaning

C. clean

D. A & C

7. You have to work ____________  for the coming exam.

A. hardly

B. more hardly

C. more hard       

D. hard

8. I had two copies of it originally, but I can’t find ____________ one now.

A. another

B. the other

C. the others 

D. other

9. Neither the boy’s parents nor I ___________________satisfied with his progress.

A. are

B. am

C. have

D. has

10. I remember ___________  him somewhere, but I can’t tell where it was.

A. to see

B. seeing

C. to be seeing

D. be seen

11.  She is wearing a ________________.

A. short nice nylon skirt                

            B. nice short nylon skirt     

C. nylon short nice skirt     

          D. nylon nice short skirt

12. My brother feels ___________  again after his operation.

A. strong

B. strongly

C. strength

D. enough strong

13. “Would you like to go to the movies tonight ?”.

 - “I’m sorry. I can’t. I ___________ my homework this evening”.

A. do

B. will do

C. doing

D. am doing

14. He does morning exercise regularly  __________  improve his health.

A. in order for

B. so as to

C. so that

D. B & C

15. We must be quick. There is   ___________  time left.

A. little

B. few

C. much

D.many

16. “ May I help you?” – “___________”

A. What can I do for you?

C. How can I help you?

B. I’m afraid I’m busy now

D. Yes. That is very kind of you.

17. I saw him ___________ the flowers in the garden.

A. watering

B. watered

C. be watered

D. be watering

18.  Ninety kilometers ___________  a long distance to drive a car.

     A. is

B. are

C. be

   D. to be

19. I remember ___________ her a five thousand dong coin yesterday.

     A. to give

B. gave

C. giving

   D. given

20. We had better use public buses to work __________ motorbikes.

     A. on behalf of

B. instead of

C. thanks to

   D. because of

III. Complete the passage with the correct form of the words in brackets.

            The Cotswolds is an area of great (beautiful)(1) ... in England. It has a number of (delight)(2)…… villages and small towns with (love)(3)….. old building that have remained unchanged since the area was the major (commerce) ……(4)…… center several centuries ago. The countryside in the area is (charm)(5)…. and most of the buildings there are made from an (attract) ……(6)…. type of light stone that is particular to the Cotswolds.

            In the summer, the Cotswolds can get rather (crowd) ……(7)…. but it is always possible to find pretty places that do not have the (famous) .

(8)…. of the more well – known villages and town. There is no shortage of pleasant hotels and (tradition) ……(9)…. inns for visitors to stay in and the Cotswolds area is an excellent place for an (enjoy) ……(10)…….weekend or long trip.

Your answers:

IV. Find a mistake in the following sentences and correct it.

Eg: We is interested in listening to Rock music.                => A -> are

            A                 B            C                                      D

1.

 People think computers never do any mistakes, but in fact, they do.

        A                                        B                                   C          D

2.

The youth nowadays prefer pop music than traditional music.

            A            B                                  C            D

3.

Hanh hated to be laughed at when he was a child.

               A        B            C                D

4.

After said goodbye to my parents, I went to school with my close friends.

A                         B                                C                            D

5.

The harder you learn, the most knowledge you get.

                            A          B               C                D

6.

Susan was very pleasing with the birthday present her father gave her.

                A                    B   C                                                         D

7.

I’m glad that you’ve done lots of progress this semester.

A                              B       C D

8.

It’s kind for you to help me with my study

A            B          C                D

9.

Every Sunday, the Petersons eat bacon and eggs of breakfast.

                                              A        B               C           D

10.

Fortunate, Nga still had enough time to finish her test.

   A                            B                     C                D

V. Put the correct tense or form of the verbs in the parentheses.

1.

- “Would you like me (go) ___(1)___ with you” I said to her

- “I’d rather (go) ___(2)___ alone.” He answer

2.

I (not see) ___(3)_ my cousin for a month. He (not go) ___(4)___  out since he (buy) ___(5)___  a new color TV.

.

You should practice (speak) ___(6)___  English every day

4.

Look at those black clouds. It (rain) ___(7)___  .

5.

A letter (send) ___(8)___  to my friend in London last week ?

6.

Do you understand what we (talk) ___(9)___  about?.

7.

The flight A30 to Da Nang City (take off) ___(10)___ at 17.00  tomorrow afternoon

Your answers:

VI. Fill in each blank with one suitable preposition.

1. We are traveling to railway station _______   his car.

2. She is tired _______   living in the city.

3. My new house is different _______  my old house.

4.  This restaurant is famous _______   Chinese food.

5. I’m always busy. I must work _______   early morning until night.

6. Bobby started school _______   the age of five.

7. This apartment is suitable_______   my family.

8. The ambulance will be there _______   about 5 minutes.

9. Don`t use that dictionary. It is _______ date. Find one that is up to date..

10.  Na got up late this morning because her alarm clock didn’t go _______ .

7
14 tháng 12 2023

Giúp mình với ạ :((

 

17 tháng 12 2023

I. Choose the word whose underlined part is pronounced differently from that of the others. 

1.

A. switch      

B. stomach

C. match

D. catch

2.

A. laughs

B. cars

C. stops

D. works

3

A. chalk

B. ship

C. machine

D. champagne

4

A. honest

B. honor        

C. hour

D. homework

5.

A. watched

B. reduced

C. coughed

D. raised

6

A. host

B. cold

C. short

D. close

7

A. sound

B. suggestion

C. island

D. selection

8

A. thirsty

B. guitar

C. dirty

D. listen

9

A. debt          

B. public

C. climber

D. thumb

10

A. effective

B. of

C. deaf

D. favorite

 

Mở ảnh

1
AH
Akai Haruma
Giáo viên
6 tháng 2

Ảnh bị lỗi hiển thị rồi bạn. Bạn xem lại nhé.

14 tháng 12 2023

\(a^2-b^2=(a-b)(a+b)\)

14 tháng 12 2023

Nồng độ %? hoặc 500 ml dd HCl

\(n_{CaCO_3}=\dfrac{30}{100}=0,3mol\\ CaCO_3+2HCl\rightarrow CaCl_2+CO_2+H_2O\\ n_{HCl}=0,3.2=0,6mol\\ \left[{}\begin{matrix}C_{M_{HCl}}\\C_{\%HCl}=\dfrac{0,6.36,5}{500}\cdot100=4,38\%\end{matrix}\right.=\dfrac{0,6}{0,5}=1,2M}\)