21. He _________to the cinema often.

A. don’t goes                      B. doesn’t goes                      C. doesn’t go                         D. don’t go

22. How _________ your father _________to work?

A. do – travel                      B. is - travel                          C. are – travel                   D. does – travel

23. You should _________ physical exercise regularly.

A. have                                B. talk                                    C. play                                  D. do

24. 8. _________ Bobby often ________ physics experiment after school?

A. Does – do                       B. Is – do                                C. Does – doing                   D. Is – does

25. We _________ to the judo club twice a month.

A. go                                    B. have                                   C. make                                D. take

26. 21. What time does Nga ________ every morning?

A. gets up                            B. get up                                 C. get                                    D. gets

27. ________ is your brother? __ he is thirteen.

A. What time                      B. How far                             C. How old                           D. How long

28. Nam ________ football now. He’s tired.

A. doesn’t play                   B. plays                                  C. is playing                   D. isn’t playing

29. School ________ at 4.30 pm every day.

A. finish                              B. finishes                              C.  D. go                               D. have

30. I often ________ my homework ________ school.

A. study – at                        B. am doing – after               C. do – after                     D. does – before

em muốn mở cánh cửa số 15 cô ạ

 Em tham gia nhận quà cánh cửa thần kì của Olm

em muốn mở cái cánh cửa số 15

1.Ha Long Bay beautiful Viet Nam

2.Mexcico City big the world

3.Yen Binh beautiful than Lang Son

4.She get and have big breakfast

5.He often swimming hot summer

(-1) + 3 + (-5) + 7+ .... + x =600 
Gọi n là số số hạng của dãy số ở vế trái: 
Ta chia thành cặp, mỗi cặp là hai số liền nhau, như vậy giá trị của mỗi cặp là 2 : 
Ta có: 2(n : 2) = 600

 $\Rightarrow$n = 600 
Mặt khác, ta có: 
(x -1) : 2 + 1 = n 

$\iff$ (x-1) : 2 +1 = 600 
$\iff$ x -1 = 599 . (2) 
$\iff$ x = 1199

2+(-4)+............+(-x)=-2000

=>[2+(-4)]+...........+[(x-2)+(-x)]=-2000

=>(-2)+..............+(-2)=-2000(có x:2 số -2)

=>(-2).(x:2)=-2000

=>x:2=(-2000):(-2)

=>x:2=1000

=>x=1000.2

=>x=2000

284,6

40

3000