2. are -> is
by him, by them, by her,... có thể bỏ.

Còn lại đúng rồi.

31. D
32. A
33. A
34. B
35. C
36. B
37. D
38. B
39. B
40. C

play - played
watched -  watched

agree - agreed

 like - liked

love - loved

carry - carried

study - studied

stop - stopped

 permit - permitted

visit - visited
edit - edited
end - ended

watch - watched
finish- finished
talk – talked

walk – walked

use – used

work – worked

cry – cried

listen – listened

- Ơ sao lại thành 2 lần nhỉ ?

1. dictionary
2. calculator
3. notebook
4. schoolbag
5. eraser
6. pencil case

18. D

a) `A=2x+1-x^2`

`=-(x^2-2x-1)`

`=-(x^2-2x+1)+2`

`=-(x-1)^2+2`

Có: `-(x-1)^2 <= forall x => -(x-1)^2+2 <=2`

`=> A_(max)=2 <=> x=1`

b) `B=4x-4x^2-5`

`=-(4x^2-4x+5)`

`=-(4x^2-4x+1)-4`

`=-[(2x)^2-2.2x.1+1^2]-4`

`=-(2x-1)^2+4`

`=> B_(max)=4 <=> x=1/2`

Câu trên đúng rồi.

Câu dưới: The last time we met our teacher was 10 years ago.