Các số nguyên dương thỏa mãn tính chất trên là 7− chỉnh hợp loại (3, 2, 2). Như vậy ta có 7!/3!2!2! = 210 số nguyên dương.

Because of being born in Doc So craft village, she knows the process of making pottery

1 is singing 

2 go

3 likes-like

4 are staying

5 reads

6 is running

7 listens - isn't listening

8 is-is-is watching

9 are they going

10 are

11doesn't go

12 go-go

13 is writing

14 have-go

15 have 

16 have

17 am eating-are playing

18 is looking-is eating

19 are

20 Does-walk

21 is- are learning

22 are you doing

23 Does-walk

24 don't play

25 Is-working

26 is doing

27 are playing-play

28 is-living

29 teaches-is teaching

30 is studying

câu 5 viết gì vậy bạn?

1. Minh lives in a house near a lake

2 There is a big yard in front of uor school

3 Are there many flowers tothe right of the museum

4 What a store is there next to the photocopy

6 How many people are there in Linh's family

7 My family doesn't live in Hanoi with his friend

8 Hoa gets up at six o'clock and brushes her teeth

9 Our classroom is on the first floor

10 There are six rooms in Minh's house

1 D

2 A

3 C

4 C

5 C

Tìm số hữu tỉ a,b,c thỏa mãn 1<a<b+c<a+1 và b<c. Cmr b<a

II

1 has seen

2 have finished

3 have lived

4 has just washed

5 have dicussed

6 has never been

7 have known

8 have learnt

9 have been

10 have stayed

1. have never watched   

2 watched

3 has read

4 had

5 had

6 have had

7 haven't seen;saw

8 rang

9 met;became

10 hasn't drunk

1D       2A          3C       4C       5C