\(\left|9+x\right|=2x\)

* Nếu 9 + x \(\ge\)0 thì x \(\ge\) -9. Ta có:

9 + x = 2x

\(\Leftrightarrow\) x + 2x = 9

\(\Leftrightarrow\) 3x = 9

\(\Leftrightarrow\) x = 3 ( Thỏa mãn )

* Nếu 9 + x < 0 thì x < - 9. Ta có :

- 9 - x = 2x

\(\Leftrightarrow\) - x - 2x = 9

\(\Leftrightarrow\) -3x = 9

\(\Leftrightarrow\) x = -3 ( Loại )

Vậy phương trình có nghiệm là x = 3

Muốn rút gọn phân thức đại số ta có thể :

+ Phân tích tử và mẫu thành nhân tử ( nếu cần ) để tìm nhân tử chung.

+ Chia cả tử và mẫu cho nhân tử chung.

Rút gọn phân thức :

\(\dfrac{8x-4}{8x^3-1}\)\(=\dfrac{4\left(2x-1\right)}{2x^3-1}\)\(=\dfrac{4\left(2x-1\right)}{\left(2x-1\right)\left(2x^2+2x+1\right)}\)\(=\dfrac{4}{4x^2+2x+1}\)

_ Hình bình hành là tứ giác có các cạnh đối song song.

_ Hình chữ nhật là tứ giác có bốn góc vuông.

_ Hình thoi là tứ giác có bốn cạnh bằng nhau.

_ Hình vuông là tứ giác có bốn góc vuông và có bốn cạnh bằng nhau.

1. Thank you very much for your letter which arrived few days ago.

2. It was lovely to hear from you.

3. I'm sorry that I haven't written for a long time but I was very busy.

4. As you knew, we bought our new house in September.

5. It was a very bad condition and it needs repairing a lot.

6. We have just finish most of it and now it looks very nice.

7. Peter and I decided to give a house - warming party on May 3rd.

8. Do you think that you will be able to come ?

9. Please give me a ring and let me know if you can come.

10. I'm really looking forward to seeing you again.

1. A. His

2. B. nurse

3. C. the tallest

4. A. writting

5. D. taken along

6. C. sporty

7. D. or

8. C. to hear

9. D. cost

10. A. how

1. Is your mother a teacher ?

2. I'm a student.

a) Chess is played for around two thousand years.

b) We plan to contact the doctor early tomorrow morning.

c) Which programme will you watch at 9p.m tomorrow ?

d) By the time we got to the cinema, the film was starting.

1. It is bad for your teeth to eat too much sugar.

2. The storm prevented him from going.

3. It took her thirty minutes to dance.

4. Nobody in my class is as tall as her.

5. The student borrowed a dictionary in order to look up the new words.