Chứng minh rằng:

\(x^2+y^2+z^2\ge\frac{\left(x+y+z\right)^2}{3}\)

Chứng minh:

ab + bc + ac \(\le\) (a + b + c)²

Nhằm động viên khen thưởng các em đạt danh hiệu "học sinh giỏi cấp thành phố" năm họ 2018-2019, trường THCS A tổ chức chuyến tham quan ngoại khóa tại một điểm du lịch với mức giá ban dầu là 375000 đồng/người. Biết công ty du lịch giảm 10% chi phí cho mỗi giáo viên và giảm 30% chi phí cho mỗi học sinh. Số học sinh tham gia gấp 4 làn số giáo viên và tổng chi phí tham quan sau khi giảm giá là 12487500 đồng. Tính số giáo viên và số học sinh đã tham gia chuyến đi

IX. Complete the text with a verb from the box in the Past Simple.

Gary Smith yesterday celebrated his twentieth birthday, but he's lucky to be alive. In March this year, he was climbing Ben Nevis, Britain's highest mountain, when he (1).................. his way and (2)................ sixteen hours in sub-zero temperatures.

My friends (3) ............... at me for having so much survival equipment, but it (4)................ my life.

On the first night, the weather was so bad that it tore his new mountain tentto pieces, so he moved into a Youth Hostel. He (5)................. the hostel at 10.00 the next morning, but that afternoon he was in trouble. "I (6)............... off a rock and (7)............... my left leg. I couldn't move".

Mountain rescue teams went out to look for Gary, and (8).............. him at 9.00 the next morning. A helicopter (9)............... him to the hospital, where he (10) .............. several operations. "Next time I'll go with my friends, not on my own!" he joked.

Rảnh thì dịch hộ mình nhé, cám ơn!

VII. Put the verbs in brackets in the Past Simple or the Past Continious.

1. I (have) .......... a busy day yesterday. I (go) .......... to class in the morning. I (eat) ......... lunch with my brother after class. In the afternoon, I (write) ........ a letter to my cousin, and (meet).......... my uncle at the airport. In the evening, I (take)............ him around the city.

2. While I (walk) ............. to class yesterday morning, I (see)............. Dick. We (say)............ hello and (walk) ........... the rest of the way to school together.

3. While I (go) ............. to the cinema, I (see) .............. an acident.

4. When I (hear).............. a knock at the door last night, I (walk)............... to the door and (open)............... it. When I (open) ............. the door, I (see).............. my brother. I (say) ............ hello to him and (ask) .............. him to come in.

5. My cousin and I (watch) ................. a film on TV last nightwwhen my brother (come)................ He (watch) ............ the end of film with us.

6. They (wait)............... for me when I (arrive) ............... at the station.

7. (They/play) ................ tennis when it (start) .................. raining?

8. She (cry) .............. when she (hear) .............. the news.

9. They (drive) ............... home from the theatre when the police (stop) ............... them.

10. Everyone (become) ................. quite when the concert (begin)..............

III. Suply the correct form of the word in bold.

1. Over 600 workers were made ........... redundant (compulsory).

2. The editor welcomes ................. from readers on any subject. (correspond).

3. A foreign ................. is the one who reports on foreign countries in newspapers or on television. (correspond).

4. We are studying the .................. of the poppulation into age groups. (divide)

5. 8 is .............. by 2 and 4, but not 3. (divide)

6. Try and smile. You don't want to give peope the wrong ................ that you are not friendly. (impress)

7. There was a conflict between ................ and national interests. (region)

8. The building is used for ................ purposes. (religion)

9. The baby slept ................. (peace)

10. For the sake of .................., let;s divide the discussion into two parts (simple).

II.Fill in each gap with a word from the box.

1. A ................. is a special building made to hold the dead body of an important person.

2. Mindful of the danger of ................ storms, I decided not to go out.

3. The warm ............... favours many types of tropical plants.

4. The law states that everyone has the right to practise their own ................. .

5. Water the pkant regularly, never letting the ............... dry out.

6. The collection ................ 327 paintings.

7. English is a ................ subject at this level.

8. The violence was the result of political and ................. conflicts.

9. We ................. that she would recover from her illness.

10. The government's ................ concern is to reduce crime.