Ta có \(\left\{{}\begin{matrix}f\left(x\right)=ax-2\\f\left(5\right)=8\end{matrix}\right.\) \(\Rightarrow5a-2=8\) \(\Rightarrow a=2\)

She asked me If those exercises were difficult

\(3x^2-7x+2=0\)

\(\Leftrightarrow3x^2-6x-x+2=0\)

\(\Leftrightarrow3x\left(x-2\right)-\left(x-2\right)=0\)

\(\Leftrightarrow\left(3x-2\right)\left(x-2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}3x-1=0\\x-2=0\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=2\end{matrix}\right.\)

1. She is too young to see this film.
=> She is not old enough to see this film.
2. My uncle took me to a pop concert last month. 
=> I remember being taken to a pop concert by my uncle last month .
3. I had to spend two days traveling to that town. 
=> It takes me two days to travel to that town.
4. It was such a dirty beach that I decided not to stay. 
=> The beach was so dirty that i decided not to stay.
5. She can’t afford to go that foreign trip.
=> She doesn’t have enough money to go that foreign trip.
6. It’s ages since they heard from her. 
=> They haven't heard from her for ages.
7. The car is too expensive for me to buy. 
=> I can’t afford to buy the car.
8. Please don’t smoke in the kitchen. 
=> I’d rather you didn't smoke in the kitchen.
9. Vicky is too young to join the club. 
=> Vicky is not old enough to join the club.
10. I wrote this essay in three hours.
=> It took me three hours to write this essay.
11. How long is it since you last saw Ann?
=> When did you last see Ann?
12. You will catch a cold if you don’t keep your feet dry. 
=> Unless you keep your feet dirty, you'll catch the cold.
13. Although they weren’t experienced, they got the job.
=> Despite not being experienced, they got the job.
14. They were too excited to sleep.
=> They were so excited that we couldn't sleep.
15. We wished we hadn’t bought this house.
=> We regretted buying this house.
16. He hasn’t played basketball for 6 months. 
=> The last time he played basketball was 6 months ago.
17. She is a more careful driver than her brother. 
=> Her brother drives more carelessly than she does.
18. It’s a pity I can’t help you now.
=> I wish i could help you now.
19. She doesn’t play tennis as well as she used to.
=> She used to play tennis better than she does.
20. Because I don’t know Japanese, I can’t apply for the job.
=> If I knew Japanese, I could apply for the job.
 

\(x^2\left(x+4\right)^2-\left(x+4\right)^2-\left(x^2-1\right)\)

\(=\left(x+4\right)^2\left(x^2-1\right)-\left(x^2-1\right)\)

\(=\left(x^2-1\right)\left[\left(x+4\right)^2-1\right]\)

\(=\left(x^2-1\right)\left(x+3\right)\left(x+5\right)\)

He had bad health là một mệnh đề, không thể dùng động từ đằng sau 

a. Vì số chia hết cho 2 là số có chữ số tận cùng lá 0;2;4;6;8

mà x987 lại có chữ số tận cùng là 7 nên không có x thỏa mãn ycbt

b. Vì số chia hết cho 5 lá số có chữ số tận cùng là 0 và 5 

mà x987 lại có chữ số tận cùng là 7 nên không có x thỏa mãn ycbt

27. The author started to write a new book two months ago.

→ The author has been writing a new book for two months                                                                                                               

28. Now I regret that I did not listen to my father’s advice.

→ Now I wish I had listened to my father 's advice                                                                                                                          

29. Some people think learning English is not difficult.

→ Some people think it is easy to learn English                                                                                                          

30. He couldn’t work very hard because he had bad health.

→ He had bad health so he couldn't work very hard    

1. D

2. A

3. B

4. A

5. D