Nguyễn Ngân's Profile

1. I am terribly sorry, I thought you were a friend of Anna’s. I took…………………………………………………………………………………………… 2. Although she was busy, she managed to find the time to proofread for me. Busy …………………………………………………………………………………………… 3. I would prefer you do computer science. I’d rather …………………………………………………………………………………….. 4. He didn’t get his visa until last Monday. It was ………………………………………………………………………………………….. 5. They continued to say that I was to blame. They persisted ……………………………………………………………………………… 6. Vietnamese coffee is considered to be one of the best in the world. Vietnamese coffee …………………………………………………………………………. 7. If you asked me well in advance, I’ll be willing to work overtime. Provided you ……………………………………………………………………………….. 8. She listens more sympathetically than anyone else I know. She is a ……………………………………………………………………………………….. 9. This is the best essay I have ever written. Never ………………………………………………………………………………………….. 10. I assumed that she would learn how to take shorthand after this course. I took it………………………………………………………………………………………… 23. Use the words or phrases given to write meaningful sentences. 1. Tourism development/ lead/ soil erosion/ pollution/ waste. _________________________________________________________ 2. Tourism/ contribute/ increasing carbon footprint/ stress/ ecosystems. _________________________________________________________ 3. The infrastructure/ tourist spot/ not/ satisfy/ great demand/ during/ peak season. _________________________________________________________ 4. Tourists/ cause/ significant effect/ local habitats/ especially/ country. _________________________________________________________ 5. Tourists/ be aware/ damage/ they/ cause/ and/ tourism authorities/ take measures/ solve/ problems. _________________________________________________________ _________________________________________________________ 6. First/ tourism/ create/ jobs/ tourism industry/ and/ other sectors/ such/ retail and transportation. _________________________________________________________ _________________________________________________________ 7. However/ jobs/ created/ tourism/ often seasonal/ and/ poorly paid. _________________________________________________________ _________________________________________________________ 8. Second/ tourism/ encourage/ preservation/ traditional customs/ handicrafts/ festivals/ but/ interaction/ tourists/ also lead/ erosion/ traditional cultures/ values. _________________________________________________________ _________________________________________________________ 9. Finally/ ecotourism/ help/ conservation/ wildlife/ generating funds/ maintaining national park. _________________________________________________________ _________________________________________________________ 10. Nevertheless/ it/ also cause/ pollution/ through traffic emissions/ littering/ noise. _________________________________________________________ 

Vì (a+b+c)^2=a^2+b^2+c^2+2(ab+bc+ca)Mà (a+b+c)^2=3(ab+bc+ca)a^a^2+b^2+c^2=ab+bc+ca        1/2(2a^2+2b^2+2c^2-2ab-2bc-2ca)=01/2((a-b)^2+(b-c)^2+(c-a)^2)=0 mà (a-b)^20                                                                                                                                              (b-c)^20                                                                                                                                              (c-a)^20  Dấu = xảy ra khi a=b=c  

1/a+1/b+1/c2a+b/a(a+2b)+2b+c/b(b+2c)+2c+b/c(c+2a)

Vì 1^3+2^3=9 mà9=3=1+2 nên đpcm

a;Công cần bơm là A1=F.s=10m.s=10.500.3=15000j                                                                       b công suất có ích của máy bơm là 1500.80%=1200wnên thời gian mà máy bơm thực hiện là     t=A/P=15000:1200=12.5s                                                                                                                công thực tế mà vật thực hiện là A=P.t=1500.12.5=18750j                                                               c Đáp án câu c ở câu b

A