1. The poem "A Visit from Saint Nicholas" was written by Clement Clarke Moore.
2. Christmas songs were performed for people in town.
3. The festival was held in the yard.
4. The telephone was invented by Bell in 1976.
5. She was met 2 days ago.

ĐK: `x^2-4x+8>=0 <=> (x^2-4x+4)+4>=0 <=>(x-2)^2+4>=0 forall x`

`\sqrt(x^2-4x+8)=2`

`<=> x^2-4x+8 =4`

`<=>x^2-4x+4=0`

`<=>(x-2)^2=0`

`<=>x=2`

1. do -> does

2. doesn't -> hasn't

3. visit -> visits

1. I really wish I had invited her to the party.

2. Bill and Peter are not old enough to ride motorcycles.

3. As she was sick, she couldn't go to the movie.

4. I asked my brother if he knew where Tony was.

5. It was such a high flood that they had to live on the roofs.

comfortable

behavior

arrangement

successfully

English is believed to be an international language.

57. Lan asked me when our meeting would start.
38. My father cooks so well that we all love his food.
59. My sister wishes she were able to speak Chinese well.
60. I haven't been to Da Lat before.
61. I can't run as fast as my friend.
62. She often visits the lady whose garden is full of roses.
63. The last time the students played this game was 5 years ago.
64. Because the wind was so strong, they couldn't go jogging.
65. The fence has just been pantied white.

1. is practising
2. is having
3. is ruinning
4. is wearing
5. is watching
6. am working
7. is raining
8. is staying
9. is becoming
10. will run
11. will spend
12. aren't studying - are watching
13. Are you listening

`16xx17xx18...xx...57 = 16.17...xx...20...xx...57`

`=>` Tận cũng là số `0`.

`56abc^2-8ac=8ac(7bc-1)`

`6a(b-2)-3(b-2)=(b-2)(6a-3)`