= 1 - \(\frac{1}{2010}\)nha em

#Chúc em học tốt

\(N=\frac{1}{1.5}+\frac{1}{5.10}+\frac{1}{10.15}+...+\frac{1}{2005.2010}\)

\(5N=\frac{5}{1.5}+\left(\frac{5}{5.10}+\frac{5}{10.15}+...+\frac{5}{2005.2010}\right)\)

\(5N=1+\left(\frac{1}{5}-\frac{1}{10}+\frac{1}{10}-\frac{1}{15}+...+\frac{1}{2005}-\frac{1}{2010}\right)\)

\(5N=1+\left(\frac{1}{5}-\frac{1}{2010}\right)\)

\(5N=1+\frac{401}{2010}\)

  \(5N=\frac{2411}{2010}\)

\(\Rightarrow N=\frac{2411}{10050}\)

Circle the best word/phrase (A,B,C or D) to complete the sentences below.

1, Australia is composed of seven _____ .

A. nations      B. countries        C. states       D. capitals 

2, _____ you ever been to any English speaking countries ?

A. Do     B. Have      C. Were    D. Are

3,  What can be done to protect people from _____ disasters?

A. environment       B. environmental          C. environmentally        D. environmentalist

4, __________ should we meet on Sunday ? - Because I have to do some shopping first, then let's meet at 10 a.m

A. Why     B. Where       C. What time          D. When

5, By the time we got to the cinema, the film ______.

A. started             B. had started           C. starting             D. starts

6, A person who _______ the bagpipes is called a piper.

A. plays             B. performs            C. entertains       D. brings

7, Don't drink that water. It's ______.

A. damaged           B.dumped           C. contaminated            D. disppeared

8. The team's succes was largely ____ to her efforts.

A. because         B. due             C. since        D. although 

9. If you ______ the president, what would you do to help the environment ?

A. are        B. had been           C. were            D. have

10, - " I've passed my driving test."

      - " _____"

A. Congratulations!          B. That's a good idea.             C. It's nice of you to say so.           D. Do you ?

Circle the best word/phrase (A,B,C or D) to complete the sentences below.

1, Australia is composed of seven _____ .

A. nations      B. countries        C. states       D. capitals 

2, _____ you ever been to any English speaking countries ?

A. Do     B. Have      C. Were    D. Are

3,  What can be done to protect people from _____ disasters?

A. environment       B. environmental          C. environmentally        D. environmentalist

4, __________ should we meet on Sunday ? - Because I have to do some shopping first, then let's meet at 10 a.m

A. Why     B. Where       C. What time          D. When

5, By the time we got to the cinema, the film ______.

A. started             B. had started           C. starting             D. starts

6, A person who _______ the bagpipes is called a piper.

A. plays             B. performs            C. entertains       D. brings

7, Don't drink that water. It's ______.

A. damaged           B.dumped           C. contaminated            D. disppeared

8. The team's succes was largely ____ to her efforts.

A. because         B. due             C. since        D. although 

9. If you ______ the president, what would you do to help the environment ?

A. are        B. had been           C. were            D. have

10, - " I've passed my driving test."

      - " _____"

A. Congratulations!   B. That's a good idea.   C. It's nice of you to say so.           D. Do you ?

gọi  3 số tự nhiên liên tiếp là x-1 ; x ; x+1

ta có ( x-1) ​* (x+1) = x² -x + x -1 = x² -1

mà x² > x² -1 một đơn vị

=> điều phải chứng minh

Gọi 3 số nguyên liên tiếp là x,x+1,x+2

Ta có : *) x.(x+2)=x²+2x

            *) (x+1)²=(x+1)(x+1)=x(x+1)+(x+1)=x²+x+x+1=x²+2x+1

Suy ra  x²+2x+1 > x²+2x

=> (x²+2x+1)-(x²+2x) = 1

Vậy (x+1)² lớn hơn x.(x+2) là 1 

ơ thế nếu trong ảnh của bạn thì đoạn AC bằng BC À......

\(\frac{S_{APN}}{S_{PNC}}=\frac{AN}{NC}=\frac{1}{3}\)(chung đường cao kẻ từ P)

\(S_{PNC}=100x3=300cm^2\)

\(\frac{S_{BNM}}{S_{NMC}}=\frac{BM}{MC}\)( chung đường cao kẻ từ N). mà 2 tam giác chung đáy NM nên đường cao hạ từ B bằng đường cao hạ từ C

Vậy \(S_{PBN}=S_{PNC}=300cm^2\)(chung đáy PN, đường cao kẻ từ B băng đường cao kẻ từ C)

\(S_{ABN}=S_{PBN}-S_{PAN}=300-100=200cm^2\)\(\frac{S_{ABN}}{S_{ABC}}=\frac{AN}{AC}=\frac{1}{4}\)(chung đường cao kẻ từ B)

\(S_{ABC}=200x4=800cm^2\)

chịu đã lên lớp 6đâu mà hỏi nguời ta hả

Bài 2.Từ văn bản "Bài học đường đời đầu tiên", em rút ra được bài học cho mình là:
- Bài học về tính kiêu căng, hỡm hĩnh, xốc nổi của Dế Mèn.
- Bài học về lòng bao dung độ lượng, biết cảm thông và tha thứ của Dế Choắt.
- Bài học về cách biết kiềm chế, không nên nóng nảy, tự ái của chị Cốc.
- Bài học về lòng nhân ái, biết yêu thương giúp đỡ những người yếu hơn mình.

Bài 3a. 

• Những câu văn có sử dụng phép so sánh trong bài thơ Vượt thác là:

“Thuyền rẽ sông lướt bon bon như đang nhớ núi rừng phải lướt cho nhanh để về cho kip.”

“ Những động tác thả sào, rút sào rập ràng nhanh như cắt.”

“Dượng Hương Thư như một pho tượng đồng đúc, các bắp thị cuồn cuộn, hai hàm răng cắn chặt, quai hàm bạnh ra, cặp mắt nảy lửa ghì trên ngọn sào giống như một hiệp sĩ của Trường Sơn oai linh hùng vĩ."

"Dọc sườn núi, những cây to mọc giữa những bụi lúp xúp nom xa như những cụ già vung tay hô đám con cháu tiến về phía trước."

Ex1: Choose the best answer: Question 1: Do you know what is the cause __________ pollution? A. of            B. in       C. on      D. for Question 2: My mother has to measure blood __________ every month A. billboard        B. pressure C. groundwater D. earplug Question 3: __________ pollution is harmful or annoying level of noise, as from vehicles, industry activities, etc. A. light        B. visual C. soil D. noise Question 4: Parents should teach children not to __________ wastes on the road A. litter        B. poison C. cause D. measure Question 5: I can’t hear your voice __________ I’m wearing an earplug A. although        B. due C. however D. because Question 6: His grandfather made him __________ hard when he was small A. study        B. to study C. studying D. studied Question 7: This picture __________ the contamination of ground water. A. illustrate        B. illustrating C. illustrates D. illustrated Question 8: Could you list some non-point source __________? A. pollution        B. pollutants C. polluting D. polluted Question 9: Scientists has just come up __________ a solution to hearing loss A. to            B. on C. with D. down Question 10: If we dump a plastic into the ground, it __________ a long time to disappear. A. will take        B. take C. took D. takes Question 11: Pollutions are harmful __________ human health A. with        B. at C. to D. on Question 12: __________ water resulted in the death of many aquatic animals. A. Contaminate    B. Contaminated C. Contaminating D. Contamination Question 13: What would you do if a factory in your neighborhood __________ untreated water into the river? A. dump        B. dumped C. dumping D. dumps Question 14: Have you ever heard about the __________ of radioactive pollution? A. affects        B. effects C. pollutes D. poisons Question 15: : __________ pollution is the increase of temperature caused by human activity. A. visual        B. water C. thermal D. radioactive Ex2: Supply the correct form of the verbs in brackets 1. Lan often (do) __________ her homework. 2. They (play) __________ tennis now. 3. Lan (buy) _________ a car since 2000. 4. Minh (watch) _______ TV last night. 5. Hoa (meet) _________ Lan tomorrow. 6. Football (play) ________ by boys. Ex3: Find and correct mistakes: 1.What about watch TV?  A. What        B. about        C. watch 2.Do you mind if I listened to music?  A. mind        B. listened        C. to 3.What do you do yesterday? A. What        B. do            C. yesterday 4.My dog is different with her dog. A. is            B. with        C. her Ex4: Rewrite sentences without changing the meaning. 1. Let’s go to the zoo! What about .......................................................................? 2. Ba enjoys skipping. Ba likes .............................................................................. 3. Long should work harder. Long ought to .................................................................... 4. Would you mind opening the door? Do you mind ......................................................................? 4. I can’t tell you unless you tell me what’s wrong. (if) -> ………………………………………………………… 5. Nhung didn’t go to the cinema with her friends because her younger sister was ill. -> Because of ……  6. Eating too much sugar can result in health problem. (lead to) -> ………………………………………………………………… 7. Minh isn’t hard working, so he often gets bad marks. (if) -> ………………………………………………………… 8. I’m not you. But I think you should recycle these plastic carrier bags. (If) -> ………………………………………………………… Ex5: Use the correct form of the words given to complete the sentences. 1. This volcano is dead; it has been (ACT) _____ for more than a century. 2. The Earth would be a happy planet if human beings, animals and plants (PEACE) _____ co-existed. 3. The chemical (POLLUTE) _____from cars and factories make the air, water and soil dangerously dirty. 4. You cannot imagine how (SERIOUS) _____the area was damaged by the flood. 5.  Scotland is a ……….. land and this is noted for its rich and interesting history. (legend)

Ex1: Choose the best answer:

Question 1: Do you know what is the cause __________ pollution?

A. of            B. in       C. on      D. for

Question 2: My mother has to measure blood __________ every month

A. billboard        B. pressure C. groundwater D. earplug

Question 3: __________ pollution is harmful or annoying level of noise, as from vehicles, industry activities, etc.

A. light        B. visual C. soil D. noise

Question 4: Parents should teach children not to __________ wastes on the road

A. litter        B. poison C. cause D. measure

Question 5: I can’t hear your voice __________ I’m wearing an earplug

A. although        B. due C. however D. because

Question 6: His grandfather made him __________ hard when he was small

A. study        B. to study C. studying D. studied

Question 7: This picture __________ the contamination of ground water.

A. illustrate        B. illustrating C. illustrates D. illustrated

Question 8: Could you list some non-point source __________?

A. pollution        B. pollutants C. polluting D. polluted

Question 9: Scientists has just come up __________ a solution to hearing loss

A. to            B. on C. with D. down

Question 10: If we dump a plas into the ground, it __________ a long time to disappear.

A. will take        B. take C. took D. takes

Question 11: Pollutions are harmful __________ human health

A. with        B. at C. to D. on

Question 12: __________ water resulted in the death of many aqua animals.

A. Contaminate    B. Contaminated C. Contaminating D. Contamination

Question 13: What would you do if a factory in your neighborhood __________ untreated water into the river?

A. dump        B. dumped C. dumping D. dumps

Question 14: Have you ever heard about the __________ of radioactive pollution?

A. affects        B. effects C. pollutes D. poisons

Question 15: : __________ pollution is the increase of temperature caused by human activity.

A. visual        B. water C. thermal D. radioactive

Ex2: Supply the correct form of the verbs in brackets

1. Lan often (do) ____does______ her homework.

2. They (play) ______are playing____ tennis now.

3. Lan (buy) ___has bought______ a car since 2000.

4. Minh (watch) ___watched____ TV last night.

5. Hoa (meet) ____will meet_____ Lan tomorrow.

6. Football (play) _____is played___ by boys.

Chào em, em tham khảo nhé!

Ex3: Find and correct mistakes:

1.What about watch TV?

 A. What        B. about        C. watch => watching

2.Do you mind if I listened to music?

 A. mind        B. listened => listen        C. to

3.What do you do yesterday?

A. What        B. do => did           C. yesterday

4.My dog is different with her dog.

A. is            B. with => from        C. her

Ex4: Rewrite sentences without changing the meaning.

1. Let’s go to the zoo!

What about going to the zoo?

2. Ba enjoys skipping.

Ba s skipping/to skip.

3. Long should work harder.

Long ought to work harder.

4. Would you mind opening the door?

Do you mind opening the door?

4. I can’t tell you unless you tell me what’s wrong. (if)

-> If you don't tell me what's wrong, I can't tell you.

5. Nhung didn’t go to the cinema with her friends because her younger sister was ill.

-> Because of her illness, Nhung didn't go to the cinema with her friends.

6. Eating too much sugar can result in health problem. (lead to)

-> Eating too much sugar can lead to health problem.

7. Minh isn’t hard-working, so he often gets bad marks. (if)

-> If Minh were hard-working, he wouldn't get bad marks.

8. I’m not you. But I think you should recycle these plas carrier bags. (If)

-> If I were you, I would recycle these plas carrier bags.

Ex5: Use the correct form of the words given to complete the sentences.

1. This volcano is dead; it has been (ACT) inactive for more than a century.

2. The Earth would be a happy planet if human beings, animals and plants (PEACE) peacefully co-existed.

3. The chemical (POLLUTE) pollutant from cars and factories make the air, water and soil dangerously dirty.

4. You cannot imagine how (SERIOUS) serious the area was damaged by the flood.

5.  Scotland is a legendary land and this is noted for its rich and interesting history. (legend)

Chúc em học tốt và có những trải nghiệm tuyệt vời tại olm.vn!

Vì \(SA\perp\left(ABC\right)\Rightarrow BC\perp SA\)(1)

Vì tam giác ABC cân tại A , M là trung điểm BC \(\Rightarrow BC\perp AM\)(2)

Từ 1,2 => \(BC\perp\left(SAM\right)\)( ĐPCM)

S B C A M

Vì \(SA\perp(ABC)\Rightarrow BC\perp SA\)

Theo giả thiết tam giác \(ABC\)là tam giác cân tại \(A\)và\(M\)là trung điểm \(BC\)\(\Rightarrow BC\perp AM\)

Ta có \(\hept{\begin{cases}BC\perp SA\\BC\perp AM\end{cases}\Rightarrow BC\perp\left(SAM\right)}\)

SA vuông góc với (ABC)=> SA vuông góc với BC

                                       mà AB vuông góc với BC ( tam giác ABC vuông) 

=> BC vg góc với (SAB)=> BC vg góc AH

                                   mà AH vg góc SB

=> AH vg góc (SBC)=> AH vg góc SC

SA vg (ABC)=> SAB,SAC vuông

SA vg BC, AB vg BC => BCvg (SAB) =>SB vg BC=> SBC vuông

vậy all mặt đều vuông

\(\hept{\begin{cases}SA\perp\left(ABC\right)\\AB\subset\left(ABC\right)\end{cases}}\) \(\Rightarrow SA\perp AB\Rightarrow\)    tam giác SAB vuông (1) 

\(\hept{\begin{cases}SA\perp\left(ABC\right)\\AC\subset\left(ABC\right)\end{cases}\Rightarrow AC\perp SA\Rightarrow}\)    tam giác SAC vuông (2) 

Tam giác ABC vuông tại B (gt) (3) 

\(\Rightarrow AB\perp BC\)   

\(\hept{\begin{cases}SA\perp\left(ABC\right)\\BC\subset\left(ABC\right)\end{cases}\Rightarrow SA\perp BC}\)    

\(\hept{\begin{cases}AB\perp BC\\SA\perp BC\end{cases}\Rightarrow\hept{\begin{cases}BC\perp\left(SAB\right)\\SB\subset\left(SAB\right)\end{cases}\Rightarrow}SB\perp BC\Rightarrow}\)    Tam giác SBC vuông (4) 

 \(\left(1\right);\left(2\right);\left(3\right);\left(4\right)\Rightarrowđpcm\)