1. If I had known you were coming to HN, I wouldn't have gone on holiday.

2. If he spoke more clearly, we could understand him.

3. If you had asked me, I would have explained it to you.

4. If Laura came, she could help us.

5. If I didn't have to study, I could go to the movie with u.

6. If they lent me the money, I would go into business right away. 

7. If we had had their phone number, we could have called them.

8. If I hadn't known George wanted to get up early, I would have woken him.

9. If Jim hadn't lent me the money, I wouldn't be able to buy the motorbike .

``

1. took - was drinking

2. saw - was waiting

3. went - was writing

4. were sitting - started

5. was cooking - were playing

6. met - was doing

7. was paying - heard

1. lost

2. have played

3. haven't bought  

4. Has she already played

5. moved

6. Did Peter speak

7. has he lost

8. finished 

``

Áp dụng tính chất của dãy tỉ số bằng nhau:

`x/2=y/(-5)=(x-y)/(2-(-5))=(-7)/7=-1`

`=>x=-1.2=2`

`y=-1.(-5)=5`

Vậy...

1. C

2. B

3. D

4. B

5. A

6.A

7. C

8. A 

9. C

10. A

11.D

11. A

12. C

13. C

14. C

15. A

16. B

18. B

19. B

20. C

1. F
2. F
3. T
4. F
5. T  

1. Listening to music in free time is my favorite hobby.
2. My brother enjoys playing piano when he was young.
3. Going to bed early and doing exercise regularly are good for health.  
4. People in Japan eat lots of tofu and fish. 
5. Jogging makes you stronger and reduces stress
6. My daughter doesn't like flower-arranging because it is an expensive hobby.

A

Ta có: \(\left\{{}\begin{matrix}\left(1-x\right)^2\ge0\forall\text{x}\\\left(x-y\right)^2\ge0\forall x\\\left(y-z\right)^2\ge0\forall x\end{matrix}\right.\)

`=>(1-x)^2+(x-y)^2+(y-z)^2>=0\ AA\ x`

Dấu "`=`" xảy ra `<=>{(1-x=0),(x-y=0),(y-z=0):}`

`<=>{(x=1),(x=y),(y=z):}`

`<=>x=y=z=1` 

`=>` ĐPCM

``

B