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Nguyễn Công Tỉnh

Điểm hỏi đáp: 10345

Ngày 10 - 07
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Những câu trả lời của Nguyễn Công Tỉnh:

Vào lúc: 2020-05-18 19:55:50 Xem câu hỏi

Gọi thời gian, vận tốc mà Hồng đi từ A đến B là : t1 , v1

thời gian, vận tốc mà Hà đi từ A đến B là : t2 , v2

Do 2 bạn đến B cùng lúc với nhau

=> t1  = t2 + 2

=>s/v1 = s/v2 +2

=> s/15 = s/20 + 2

=> s =60 (km)

Vào lúc: 2020-05-18 19:17:42 Xem câu hỏi

c, Theo phần b có , tgiac AHD đồng dạng tgiac CED

=? HD/ED = AD/CD

 Xét tgiac HDE và tgiac ADC, có:

 góc HDE = góc ADC ( 2 góc đối đỉnh)

HD/ED = AD/ CD (cmt)

=> tg HDE đồng dậng tg ADC ( c.g.c)

d, Áp dụng định lý Pytago vào tg ABC , có:

BC^2 = AB^2 + AC^2 = 6^2 + 8^2

=>BC = 10 (cm)

Có : BA^2 = BH. BC

=> BH = 3,6 = HD

=> BD = 2BH = 7,2(cm)

=> DC = BC - BD = 2,8 (cm)

Chứng minh tgiac AHB = tg AHD (c.g.c)

=> AD = AB = 6 (cm)

theo phần b, tg CDE đồng dạng th ADH

=> Dc/DA = DE/DH

=> DE = 1,68

Áp dụng đính lý pytagp vào tg CED

=> DC^2 = EC^2 + De^2

=> EC = 2,24

=> Diện tích tam giác CED = 1/2 . DE .EC = 1,8816 (cm^2)

Vào lúc: 2020-05-18 19:06:57 Xem câu hỏi

(Bạn tự vẽ hình nhé)

a,\(\text{ Xét \Delta ABC và \Delta HBA, có:}\)

\(\widehat{B}\): là góc chung

\(\widehat{BAC}=\widehat{BHA}=90^o\)(  vì tam giác ABC vuông tại A, AH vuông góc với BC)

=> tgiac ABC đồng dạng với tam giác HBA ( góc - góc)

b, Xét tam giác AHD và tam giác CED, có:

 góc HDA = góc EDC ( 2 góc đối đỉnh)

  góc AHD = góc CED =90 độ (giả thiết)

=> tgiac AHD đồng dạng tgiac CED ( g.g)

=> AH/ CE = AD/ CD

=>AH.CD = CE.AD (dpcm)

Vào lúc: 2020-05-06 15:48:32 Xem câu hỏi

\(A=\left[\frac{6x^2}{x^3-1}-\frac{2x-2}{x^2+x+1}-\frac{1}{x-1}\right]:\frac{x^2+9}{\left(x-1\right)\left(9-4x\right)}\)

\(=\left[\frac{6x^2}{x^3-1}-\frac{\left(2x-2\right)\left(x-1\right)}{\left(x^2+x+1\right)\left(x-1\right)}-\frac{x^2+x+1}{\left(x-1\right)\left(x^2+x+1\right)}\right]\cdot\frac{\left(x-1\right)\left(9-4x\right)}{x^2+9}\)

\(=\frac{6x^2-\left(2x^2-4x+2\right)-x^2-x-1}{\left(x^2+x+1\right)\left(x-1\right)}\cdot\frac{\left(x-1\right)\left(9-4x\right)}{x^2+9}\)

\(=\frac{5x^2-2x^2+4x-2-x-1}{\left(x^2+x+1\right)}\cdot\frac{\left(9-4x\right)}{x^2+9}\)

\(=\frac{3x^2+3x-3}{\left(x^2+x+1\right)}\cdot\frac{\left(9-4x\right)}{x^2+9}\)

Biểu thức A bạn viết đúng chưa?

Vào lúc: 2020-02-27 08:23:55 Xem câu hỏi

1. Although their husbands were absent,they still fulfilled their housework

--> In spite of their absent husbands ,they still fulfilled their housework

2. You are the last person to see her alive

->You are the last person who saw her alive.

3.He's too weak to walk

->He isn't strong enough to walk

4.In spite of being on a diet , she still eats a lot of chocolate

->Although she is on a diet , she still eats a lot of chocolate

5. It's too dark for her to see the way in the tunnel 

->It isn't bright enough  for her to see the way in the tunnel 

6.Although she lives a comfortable life , she's unhappy

->Despite living a comfortable life , she's unhappy

7.Here are some accounts to check (relative clause)

-> Here are some accounts that people must check

8.In spiteof high prices , my daughter insists on going to the cinema every Sat

->Although the prices are high , my daughter insists on going to the cinema every Sat

9.Although he has succeedded in his job , he isn;t satisfied

->Despite having succeedded in his job , he isn;t satisfied

10.The food is good.We can eat it (enough)

->the food is good enough for us to eat

Vào lúc: 2020-02-27 08:16:37 Xem câu hỏi

1. I'm leaving now because I don't want to miss the train. (so)

=> I................... don't want to miss the train so I'm leaving now ................................

2. The last time I saw my uncle was two years ago. (for)

=> I haven't ........seen my uncle for two years........................................

3. Let me reach my office and then I will talk to him. (when)

=> I .............will talk to him when I reach my office ................................................

4. Why don't we donate our old books, toys and clothes to charity? (when)

=> Mom ..........................................................................................

5. Jane stayed behind after the class in order to talk to the teacher. (because)

=> Jane........................stayed behind after the class because he talked to the teacher.......................

6. Where do you live? (address)

=> What ..........is your address................................................................

7. How old is she? (age)

=> What ..........is her age?...............................................

8. What time will it start? (start)

=> When .......will it start?.............................................

9. Mr. Brown is not free this afternoon. (be)

=>Mr. Brown ...........is busy this afternoon............

10. What does his sister do? (job)

=> What ............is his sister's job?....................................................

Vào lúc: 2020-02-22 17:15:09 Xem câu hỏi

1 the / in / my neighborhood / those / roads / are / narrower / than / in / their neighborhood

=>in their neighborhood, the roads are narrower than those in my neighborhood

2 think/ in / a city / is / living / more interesting / I / than / in / a country

=>I think living in a country is more interesting than in a city

3 a sofa / comfortable / is / than / more / a chair / ?

=>Is a sofa more comfortable than a chair?

Vào lúc: 2020-02-22 17:11:42 Xem câu hỏi

bài 1 :put the verbs in brackets in the correct form

1.   Last year, when we (be)were in Canada , we (go)went skiing (ski) almost every day 

2.  Did  You (watch)watch a football match on TV last night ?

3.   Where did he buy(buy) those trainers ?

4.   We (not go)didn't go out yesterday bacause it (rain)rained. We(watch)watched TV at home  

5.   When the bell rang at the end of the lesson , Lan (put)put her books away and (leave)left

Vào lúc: 2020-02-11 14:37:10 Xem câu hỏi

\(\frac{1-3x}{2}-\frac{x+3}{2}\)

\(=\frac{1-3x-x-3}{2}\)

\(=\frac{-4x-2}{2}\)

\(=-2x-1\)

Vào lúc: 2020-02-11 14:35:16 Xem câu hỏi

\(b,21-\left(-6+3x\right)=9\)

\(\Rightarrow21+6-3x=9\)

\(\Rightarrow27-3x=9\)

\(\Rightarrow3x=18\)

\(\Rightarrow x=6\)

c, -(2x+4)+11=-27

=>-2x-4+11=-27

=>-2x+7=-27

=>-2x = -34

=>x=17

d, 33-(33-x)=0

=>33-33+x=0

=>x=0

Vào lúc: 2020-02-11 14:33:00 Xem câu hỏi

b,

a là số lẻ (2k + 1)

a là số chẵn (2k)

Với a là số lẻ ,ta có :

(a - 2)(a + 3) - (a - 3)(a + 2)

= (2k + 1 - 2)(2k + 1 + 3) - (2k + 1 - 3)(2k + 1 + 2)

= (2k - 1)(2k + 4) - (2k + 4)(2k + 3)

= (2k + 4)[(2k - 1) - (2k + 3)]

Vì 2k + 4 = 2.(k + 2) chia hết cho 2

=> (2k + 4)[(2k - 1) - (2k + 3)] chia hết cho 2

=> (a - 2)(a + 3) - (a - 3)(a + 2) chia hết cho 2

Với a là số chẵn ,ta có :

(a - 2)(a + 3) - (a - 3)(a + 2)

= (2k - 2)(2k + 3) - (2k - 3)(2k + 2)

= 2.(k - 1)(2k + 3) - 2.(k + 1)(2k - 3)

= 2.[ (k - 1)(2k + 3) - (k + 1)(2k - 3)] Chia hết cho 2

Vậy với mọi a thì (a - 2)(a + 3) - (a - 3)(a + 2) chia hết cho 2 

nguồn: Câu hỏi của Nguyễn Khánh Dương - Toán lớp 6 - Học toán với OnlineMath

Vào lúc: 2020-02-11 14:31:35 Xem câu hỏi

\(\frac{2\left(x+y\right)\left(x-y\right)}{x}-\frac{-2y^2}{x}\)

\(=\frac{2\left(x^2-y^2\right)+2y^2}{x}\)

\(=\frac{2x^2-2y^2+2y^2}{x}\)

\(=\frac{2x^2}{x}\)

\(=2x\)

Vào lúc: 2020-02-11 14:30:08 Xem câu hỏi

\(\frac{3x+1}{x+y}-\frac{2x-3}{x+y}\)

\(=\frac{3x+1-2x+3}{x+y}\)

\(=\frac{x+4}{x+y}\)

Vào lúc: 2020-02-11 14:28:49 Xem câu hỏi

Tham khảo:Câu hỏi của Kiều Thị Huyền - Toán lớp 6 - Học toán với OnlineMath

Câu hỏi của Thinhdc6a5 - Toán lớp 6 - Học toán với OnlineMath

Vào lúc: 2020-02-11 14:26:44 Xem câu hỏi

Viết lại câu mà nghĩa ko đổi :
1. Do you want a glass of lemonade?

=> Would you _____li ke a glass of lemonade __________?.

2.What is the price of a cake and an orange?

=> How_______much are a cake and an orange____________?
3. My house is behind the hotel.

=> The hotel _____is in front of my house__________.
4.What about going for a swim? It’s very hot today.

=> Why _______don't we go for a swim ___________?

5.Coffee is her favorite drink.
=> She ______li kes drinking coffee___________.

Vào lúc: 2020-02-11 14:25:16 Xem câu hỏi

Dùng từ gợi ý để vt thành câu:

1. Ho Chi Minh city/ a population / 3.5 million.
=>........Ho Chi Minh City has a population of 3.5 million..............

2.Daewoo Hotel / tall building / our town.
=>................Daewoo Hotel is the tallest building in our town.........
3.He / want/ travel / train

=>................. He wants to travel by train..............................
4.There / be / bookstore / opposite / school?

=>………There is a bookstore opposite to the school.………………

Vào lúc: 2020-02-11 14:21:40 Xem câu hỏi

III Choose the word whose underlined part is pronounced differently from the others

1. A. arrived B. stayed C. received D. hoped

2. A. opened B. knocked C. played D. called

3. A. rubbed B. earned C. stopped D. filled

4. A.prefered B. travelled C. passed D. stirred

5. A. tipped B. begged C. quarreled D. carried

6. A. tried B. obeyed C. cleaned D. asked

7. A. packed B. added C. worked D. pronounced

8. A. watched B. phoned C. referred D. followed

9. A. agreed B. needed C. smiled D. loved

10. A. laughed B. washed C. helped D. weighed

Vào lúc: 2020-02-11 14:20:07 Xem câu hỏi

1.I know the.....to the post office

a.book    b.lunch      c.walk       d.way

2.why didn't you go camping last week?If you....there,you would have had a lot of fun.

a.were being   b.have been       c.had been     d.was being

3.his trick made me furious

a.extremely angry      b.hot           c.not very happy          d.too sad

4.-will you do me a favour?

   -yes......great pleasure.

a.at        b.of             c.with             d.in

5.what......if you had a day off yesterday?

a.would you have done              b.would you do

c.will you do                     d.you would have done

6.can you...me a good french restaurant?

a.recommend                 b.praise                c.say about              d.answer

7.he will....his brother to the zoo with him

a.give                  b.take                   c.                    d.catch

8.long is working in a bicycle firm.he...there since 1978

a.had worked                        b.has been working

c.were working              d.was working

Vào lúc: 2020-02-11 14:18:29 Xem câu hỏi

1.she often hires the van to transport her goods

a.the heavy car               b.the coach

c.the small truck              d.the big motorbike

2............everything before the visitors came?

a.had they prepared                b.were they preparing

c.have they prepared                 d.are they preparing

3.the boys were clapping their hands and cheering loudly

a.enjoying himself                     b.crying louldy

c.observing the scene                     d.shouting congratulations

4.what games did you .......?

a.best            b.well              c.rather                    d.better

5.will you...me how to play tennis?

a.learn            b.call                c.need              d.show

6.I.....that he was an english teacher

a.am thinking                   b.thought

c.am being thought                    d.was thinking

7.there are only ordinary flowers in this garden.

a.common           b.good-looking                 c.famous              d.gently

8.this is a good athlete....performance is admired by many  people in the word.

a.whom               b.which                 c.whose                  d.who

9.the ball...the fence and into the classroom.

a.hit     b.shot      c.kicked               d.went over

10.the test becomes.....and......

a.hard / hard                     b.harder / harder

c.hardest/hardest              d.harder/hard           

Vào lúc: 2020-02-10 22:13:11 Xem câu hỏi

Điền giới từ thích hợp :
1. What _______about_____ playing table tennis ?
2 .She is __on_____ vacation in Ha Long Bay.
3.Nga always helps her mother ___after___school
4. I'm very busy now. Can you go to the store ________for_____me ?
5.I live in a house ___in____ the country

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