Cho tam giác ABC có AB = b , AC = c, BC = a . Tại sao c/a + a/c + b/c + c/b + b/a + a/b = 6 ạ

Đến nửa sau thế kỉ XIX, việc phát minh ra phương pháp nào trong luyện kim đã dẫn đến sự ra đời của các nguyên liệu mới?

cho tam giác ABC có A(1;2),B(-3;-1),C(3;-4).tìm điều kiện của tham số m để điểm M(m;m-5/3) nằm bên trong tam giác ABC

Bài 2
Hình thang ABCD(AB//CD).Gọi M,N lần lượt là trung điểm của AB và BC đoạn thẳng MN cắt BD tại E,cắt AC tại F
a,Chứng minh ME=NF=1/2AB
b,Chứng minh È=CD-AB:2

Bài 28 : Có một xe máy bắt đầu đi từ A đến B với vận tốc 40 km / giờ , sau 3 giờ lại có một ô tô đi từ A đến B với vận tốc 60 km / giờ . Sau bao nhiêu lâu hai xe gặp nhau .

Tính: 2-4-6+8+10-12-14+16+...+98-100-102+104
 

Bài 1: Thêm từ ngữ, hình ảnh để các câu sau có sử dụng nghệ thuật so sánh hoặc nhân hóa:

- Gió.............

- Cổng trường..............

- Sân trường............

- Các lớp học.............

- Các bạn học sinh................

- Tiếng chim hót..........

- Tiếng nói chuyện cười đùa..........

- Mùi huonhw của các loài hoa trong vườn hoa............

- Tiếng trống..........

tìm số có 2 chữ số lớn hơn 4 lần tổng chữ số của nó là 15 . Nếu cộng thêm 3 vào số đó thì được số mới . Số này nhỏ hơn số có 2 chữ số như ban đầu nhưng ghi theo thứ tự ngược lại

Cần gấp cần gấp please huhu

1.      I want (stay)......................... at home tonight.

2.      The students started (learn).................................. at 7.00.

3.      At last they agreed (help).........................him

4.      I prefer (watch) .............................. film to listening to music.

5.      You should turn off the lights before (go) .............................. to bed.

6.      We didn’t know where (play)………………………….. football.

7.      The doctor advised me (drink)...........................more water every day.

8.      Our parents always hope us (get)..................high marks on high-school entrance exam.

9.      Would you mind (open) .............................. the windows?

10.  Everybody was anxious (know).............what had happened.

11.  I am afraid (go).....................out at night.

12.  It is very pleasant (talk).................to you.

13.  I am glad (meet)...........................you.

14.  You have to learn hard so as (pass)..........................your exam.

15.  It is very kind of you (say)..................................so

16.  He is strong enough (carry)............................this bag.

17.  It takes me three hours (do).........................my homework every day.

18.  The weather was too bad for us (have)..........................a picnic

19.  It is dangerous (lean)..............................out of the window.

20.  We have difficulty in (learn).............................. English.

21.  I sometimes make my parents (feel) .............................. sad.

22.  You are too young (understand)....................what is happening.

23.   His plan is (keep)..............................the affair secret.

24.  Mr. Nam is always busy (work) .............................. on the farm.

25.  My father started (drive) .............................. a car 2 years ago.

26.  This room is dirty. It needs (clean) ..............................

27.  He made me (move) ................................... his car.

28.  The weather was not fine enough for us (go).............................camping.

29.   My elder brother wished (pass)........................the university entrance exam.

30.  I can’t help (sneeze) .............................. I caught a cold yesterday.

31.  He often has his wife (prepare) .............................. meals.

32.  Is your mother interested in (cook) ..............................?

33.  I used to get up early in order (learn)..................................new words by heart.

34.  Instead of (feel) .............................. sorry for yourself, do some work for charity.

35.  Do you mind if I (smoke) .............................. here?

36.  Although he had a broken leg, he managed (get)..............out of the car.

37.   He intended (buy)..............................an expensive house.

38.  You had better (say)........................ nothing.

39.  Last year we spent two days (stay) .............................. in Ha Long Bay.

40.  My former teacher always encouraged me (study)...........................better.

41.  My father taught me (ride)...................a bike when I was small.

42.  Please stop (talk)............................... I am trying (finish) ............................. a letter.

43.  It’s high time for you (study) .......................... harder.

44.  I am looking forward to (receive) .............................. your letter.

45.  Let’s (help) ................. the poor in our village.

46.  Don’t forget (write) ..................... me a letter.

47.  My father enjoys (fix) ........................... things at home.

48.  This film is worth (watch) .............................. because it is very interesting.

49.  It is no use (read) .............................. that novel. It is boring.

50.  I am used to (get) .............................. up early every morning.

51.  What did you use (eat) .......................... when you were small?

52.  My younger sister cannot (speak).......................

53.  The police let the thief (go) .............................. away.

54.  (Collect) ..............................stamp is her hobby.

55.  He suggested (use).............................. banana leaves to wrap things.

56.  (Lie) .....................on the beach is much more pleasant than (sit) ...........................in the office.

57.   The doctor advised me (not smoke) ............................. a lot.

58.  How about (play) .............................. soccer in the school yard?

59.  Did you get used to (drive) .............................. on the left?

60.  I found it difficult (park) .........................

61.  I found (park)…………………………… difficult.

62.  Tourists could see fish (swim)………………… along the brook.

63.  We enjoy (swim)………………… along this river.

64.  The form teacher has asked Jack (write) …………………an essay on the Thames.

65.  It sometimes may be difficult (get)………………… a taxi during rush- hours.

66.  The rain has made the children (stop)………………… their games.

67.  She tells the driver (take)…………………….. her to the railway station.

68.  Does Mrs. Green have them (carry) ………………………those books back home?

69.  The principal noticed those pupils (try)…………………….. harder and harder.

70.  Children have just stopped (play)……………………….. football.

71.  They keep (talk)…………………………… about an old friend they met yesterday.

72.  Is Black Pool (visit)…………………………. by thousands of tourists each year?

73.  We heard Mr. Brown (park)……………………….. his car near the gate.

74.  They’ve finished (do)……………………………..their homework.

75.  They had their house (paint)……………………….. before Tet holiday.

76.  I advised him (wait)………………………………. for me at the airport.

77.  Would you mind (help)……………………………. me with this work?

78.  Do you smell something (burn)………………….. in the kitchen?

79.  Mother requests her daughter not (come) ……………………back home late.

80.  We shall have the grass (cut)……………………. tomorrow.

81.  They noticed lots of sheep (graze)……………………. in green meadows.

82.  Would you like (have)………………………… something to eat?

83.  It started (rain)……………… an hour ago. Has it stopped (rain)………………… yet?

84.  My family is trying (decide)……………………where to go on holiday.

85.  Our teacher made me (answer)……………….all the questions.

86.  I hate (see)…………………. a child (cry)………………………...

87.  They prefer (play)………………………… in swimming pool all day.

88.  They refuse (go)……………………….. out on trips if it’s too hot.

89.  I used (smoke)………………… 20 cigarettes a day, but now I give up (smoke)…………

90.  We decided (rent)……………………… a house with a swimming pool.

91.  Can you help me (get)……………………. the dinner ready?

92.  When we arrived, the people next door invited us (have)……………a drink with them.

93.  We began (talk)……………………………. about next year’s holiday two months ago.

94.  I remember (lock)…………. the door when I left but forgot (shut) ………… the window.

95.  He agrees (start)…………………………… the job as soon as possible.

96.  I finished (read)………………………….. the book and went to bed.

97.  My teachers always expected me (do)………………………………….. well in exams.

98.  Let me (pay)………………………………….. for the meal. You paid last time.

99.  It’s difficult ( get)…………………..used to ( eat)………………………… with chopsticks.

100.           I have my mom (wash)………………………..my clothes every day.

Tìm nZ,sao cho a)14n-16 chia hết cho 2n-3

Giúp mik vs!
Tính tổng sau bằng cách hợp lí:
1) 1+5+6+11+17+...+118
2)1+5+6+11+...118
3)5+10+15+...+55
4)2+4+6+...+48

Đồ thị hàm số $y=x^{4}-x^{2}+1$ có bao nhiêu điểm cực trị có tung độ dương?

$A.1$

$B.2$

$C.3$

$D.4$