Khối lượng NaCl có trong dung dịch nước muối sinh lý 0.9%

giúp ..................................................................................................với

A, Cot ( 3x + 10° ) = cot45° B, Cot3x=cot pi/6

giúp mình với ạ! ( hic ko phiền các bạn có thể trả lời giúp mình: • căn x.(căn x -1) <0 • )

1. He usually (work) very hard, but he (not work) at all today because it’s a holiday. 2. Look! That man (run) out of the bank. And he (carry) a large bag full of money. 3. I (watch) TV when the phone (ring) . 4. After Richard (finish) work, he (go) home. 5. By the time the firemen (arrive) , the fire (already, go out) . 6. When she (be) a child, she always (want) to do the most dangerous things. 7. Water (boil) at 100 degrees Celsius. 8. I’m sorry I (forget) to do my homework yesterday. 9. We (not see) any interesting films lately. 10. The film (begin) when we arrived at the cinema. 11. I think I (lose) my door key. I can’t find it anywhere. 12. Eric (not find) a flat yet, so he’s still living with his parents. 13. They (start) running their own company in 1980. 14. When the match was over, the spectators (go) home. 15. The phone (ring) suddenly while Joanne was doing the housework. 16. I (study) ________________ English for three years 17. Up to the present, we (write) ________________ almost every lesson in the book. 18. I (not see) ________________ him since last Monday. 19. George (work) ________________ at the university so far. 20. My father (not smoke) ________________for 5 years. 21. You (receive) ________________ any letter from your parents yet? 22. Jim sends his love. I (just, see)________________ him in the high street. 23. When the police (arrive) _____________________, the robbers had gone. 24. When I arrived the students (already, go) _____________________ into class. 25. Miss Davis (type) _____________________ letters after manager (come)__________________ back. 26. My roommate had finished dinner by the time I (get) ____________________ home. 27. They (go) _____________________ home after they (finish) _____________________ their work. 28. Before she (watch) ____________________ TV, she (do) _____________________ her homework. 29. When she (be) a child, she always (want) to do the most dangerous things.

1. My father (work)………………………. in that factory before. 2. My father (work)…………………….. in that factory before 1999. 3. Up to now, I never see) ……………………….such a fat man. 4. Up to then, I (never see)……………………………….. such a fat man. 5. It’s the first time I (eat)…………………………… this. 6. This is the worst storm I (ever see)…………………………. 7. It was the first time I (ever see)…………………………… such a beautiful girl. 8. It was the most exciting film I (ever see)……………………….. 9. This was the dirtiest looking dog I (ever see)…………………………… 10. When I came here I (find) ……………………that everything (be) ………………ready. 11. I was late. The teacher (already give)…………………. a quiz when I (get)……… to class. 12. When I (come)……………. there, she (go)……………………. away half an hour before. 13. Sam (already/ leave) ………………..…………….when we (get)……………. there. 14. My friend (not see)………………….. me for many years when I ( meet)……… him last week. 15. He (visit)…........... his friend yesterday and ( find) …………..that he ( be)……………… out.

1. What you (do) ……………….yesterday. 2. How long you (learn) …………………English? 3. Tom (never be)………………… in Daklak. 4. I (have) …………………….a little trouble with my car last week. 5. I (read) ………………….that novel by Hemingway several times before 6. She ( be) ……………so happy when she ( hear) the news that she ……………..( cry) 7. We (study) ……………..almost every lesson in this book so far. 8. I (not see) ……………….her since Last week. 9. My wife and I (travel)……………..to London last Summer. 10. They (give)……………………. me the letter a few minutes ago. 11. I (wait)…………………for two hours, but she (not come) …………………….yet. 12. He (write) ……………………. a book since last year. 13. How long you (learn) …………………..English? 14. Tom (already finish) …………………..his homework. 15. I (read) ………………………..the novel written by Jack London several times before. 16. Mai (never be) ……………………..in Hanoi. 17. She (study) …………………….. Korean for two years.

1. Sue (work) ……………………………..at ten o’clock yesterday morning. 2. What ……you (do) ……..at 4 pm yesterday?- well, I ( work)……………….. in my office. 3. At 9 last night, Mrs. Smith (wash) ………the dishes while her children (study)……………….their lesson. 4. Yesterday I ( see)…… an accident while I ( wait)……………… for you on this corner 5. While I (walk)………………. to class yesterday morning, I (see)……….. Mary. 6. When I be)…………… young, I often (go) ……………..fishing with my uncle. 7. My younger brother often (cry) ……………at night when he (be) ………………3 years old. 8. When he (be) ………………young, he listen) ……………to the radio.

2. Yesterday he (go) ………………….home late. 3. Sam (arrive) ……………..in San Diego a week ago. 4. Pasteur (die)………………. in 1895. 5. She paid for her ticket and ( leave)…………………… 6. There (be)………………….. an interesting film on TV last night. 7. I (not watch)…………………………. television last night. 8. He (not be)……………………… present at class yesterday. 9. What …………you (do)………. last Sunday? 10. I (have) …………….a little trouble with my car last week. 11. Where ………John (work)………….. two years ago?

Làm bài tập từ 1 đến 6 trong SGK/Trang 11. 3. Đọc trước phần III. Bài 2, trả lời câu hỏi: - Hỗn hợp là gì? Chất tinh khiết là gì? - Theo em, nước tự nhiên là một hỗn hợp hay chất tinh khiết?