Bài 1: Tìm các số hữu tỷ a, b, c biết:

a, ab = 3 / 5, bc = 4 / 5, ca = 3 / 4

b, a. ( a + b + c ) = -12;   b. ( a + b + c ) = 18;   c. ( a + b + c ) = 30

c, ab = c;   bc = 4a;   ac = 9b

Bài 2: Cho A bằng:

A = ( 1 / 2² - 1 ) . ( 1 / 3² - 1 ) . ( 1 / 4² - 1 ) ... ( 1 / 100² - 1 )

So sánh A với - 1 / 2

Chú ý: " / " là phân số; " . " là dấu nhân cấp 2

@Uchiha_Shisui

Bài 1: Tìm số hữu tỉ x biết:

a, ( 2x - 1 )⁴ = 81                                                    b, ( x - 1 )⁵ = -32

                           c, ( 2x - 1 )⁶ = ( 2x - 1 )⁸

Bài 2: Tìm các số tự nhiên x, y biết rằng: 

a, 2^{x + 1} . 3^y = 12^x.                                                b, 10^x : 5^y = 20^y

                                c, 2^x = 4^{y - 1} và 27^y = 3^{x + 8}

24. Mary couldn't leave the children alone_____could she_____?

25. You aren't doing anything tonight_____are you_____?

26. You wouldn't mind helping me with this_____would you_____?

27. George hadn't been there before_____had he_____?

28. The children weren't surprised_____were they_____?

29. You wouldn't like another drink_____would you_____?

30. Tom doesn't have to go to lectures_____does he_____?

31. Bill hasn't got a car_____has he_____?

32. Bill couldn't have prevented it_____could he_____?

33. I needn't wait any longer_____need I_____?

34. There weren't any mosquitoes_____were there_____?

35. The fire wasn't started deliberately_____was it_____?

36. The children can read French_____can't they_____?

37. He's ten years old_____isn't he_____?

38. Bill came on a bicycle_____didn't he_____?

39. The Smiths have got two cars_____haven't they_____?

40. Your grandfather was a millionaire_____wasn't he_____?

41. Tom should try again_____shouldn't he_____?

42. It could be done_____couldn't it_____?

43. Your brother's here_____isn't he_____?

44. That's him over there_____isn't it_____?

45. George can leave his case here_____can't he_____?

46. This will fit in your pocket_____won't it_____?

47. His wife has headaches quite often_____doesn't she_____?

48. She's got lovely blue eyes_____hasn't she_____?

49. The twins arrived last night_____didn't they_____?

50. Mary paints portraits_____doesn't she_____?

51. Bill puts the money in the bank_____doesn't he_____?

52. Prices keep going up_____do they_____?

53. I've seen you before_____haven't I_____?

54. Bill's written a novel_____hasn't he_____?

55. His mother's very proud of him_____isn't she_____?

56. The twins used to play rugby_____didn't they_____?

57. Tom might be at home now_____mightn't he_____?

58. We must hurry_____mustn't we_____?

59. You'd been there before_____hadn't you_____?

60. You'd like a drink_____wouldn't you_____?

61. The boys prefer a cooked breakfast_____don't they_____?

62. Mary ought to cook it for them_____ought not she_____?

63. That was Ann on the phone_____wasn't it_____?

64. The Smiths need two cars_____don't they_____?

65. He used to eat raw fish_____didn't he_____?

66. You'd better wait for Bill_____hadn't you_____?

67. You'd come if I needed help_____didn't I_____?

@Uchiha_Shisui

Ai biết giúp với T^T

@Uchiha_Shisui

Viết lại câu từ chủ động sang bị động

1. They started a dancing class last week

→ A dancing class was started by them last week.

2. Mr Smith saw the accident

→ The accident was seen by Mr Smith

3. Somebody has taken my briefcase
→ My briefcase has been taken

4. The teacher returned our written work to us

→ Our written work was returned to us by the teacher

5. She has finished the report by noon

→ The report has been finished by her by noon

6. The mad dog bit the little boy

→ The little boy was bitten by the mad dog

7. The police have arrested five suspect

→ Five suspects have been arrested by the police

8. The doctor ordered him to take a long rest

→ He was ordered to take a long rest by the doctor

9. They are sweeping the streets

→ The streets are being swept by them

10. The mailman had already delivered the mail

→ The mail had already been delivered by the mailman

11. He had to finish his work on time

→ His work had to be finished on time

12. You needn't do all the homework

→ All the homework needn't be done.

13. You ought to tell him early

→ He ought to be told early

14. They don't use the room very often

→ The room isn't very often used.

15. They must widen the road to school this year

→ The road to school must be widened this year.

16. Have you done your homework?

→ Has your homework been done?

17. Did you finish your work early?

→ Was your homework done early?

18. She has to pick fruit very early in the morning

→ The fruit has to be picked very early in the morning

19. The house was dirty because she hadn't clenched it for weeks

→ The house was dirty because It hadn't been clenched for weeks

20. She is taking care of the baby girl

→ The baby girl is being taken care of by her

21. Children should treat old men with respect.

→ Old men should be treated with respect

@Uchiha_Shisui

1. I advise you not to stay up late every night.

- You should not stay up late every night.

2. She didn't accept my proposal yesterday.

- My proposal wasn't accepted by her yesterday.

@Uchiha_Shisui

33 will be bought by us

34 she liked to do the quiz very much

35 It was such excellent snow that we all enjoyed it

36 3 hours going his homework

@Uchiha_Shisui

I can dance more...than my friends.

A. fluently    B. attentively   C. interesting .    D. gracefully

Giải thích vì sao bạn chọn đáp án đó nữa nhak!!!

 Giải thích: vì nó nghĩa là duyên dáng :v những cái còn lại ko hợp nghĩa.

@Uchiha_Shisui

Bước 1: Đem quả cầu kim loại đặt lên bàn cân và xác định khối lượng của nó là m

Bước 2 : Cho lượng nước vào bình chia độ đánh dấu V₁, sau đó thả quả cầu vào nước dâng lên mức V₂

Bước 3 : Xác định V_{quả cầu} = V₂ - V₁

Bước 4 : Ta tính khối lượng riêng của quả cầu bằng công thức : D = m/V_{quả cầu}

@Uchiha_Shisui