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AH
Akai Haruma
Giáo viên
9 tháng 7 2020

Lời giải:
Vì $a$ là số nguyên tố lớn hơn $3$ nên $a$ có thể có dạng $6k+1, 6k+5$ với $k\in\mathbb{N}$

Nếu $a=6k+5\Rightarrow 10a+1=10(6k+5)+1=60k+51=3(20k+17)\vdots 3$ và $10a+1>3$ nên $10a+1$ không thể là số nguyên tố (trái giá thiết)

Do đó $a=6k+1$

Khi đó: $5a+1=5(6k+1)+1=6(5k+1)\vdots 6$ (đpcm)

29 tháng 5 2021
 

The COVID-19 epidemic is a dangerous disease and they are raging in  all over the world.First, with a very high rate of spread, people will be very susceptible to infection. causing a lot of problems, it is economically difficult and causes millions of deaths, so doctors have to work day and night to be able to help patients in dangerous epidemic situations such as Therefore, everyone should wash their hands clean.Always wear a mask when going out and avoid contact with epidemic areas. I hope the epidemic will soon end so that society can live a normal life

29 tháng 5 2021

Mình cảm ơn bạn. Chúc bạn học tốt!

15 tháng 7 2021

    Covid 19 is an epidemic that has troubled many people. Our studies and lives are also affected. We are not allowed to go to school, causing us to lose knowledge. We have to learn online, although it's effective, not everyone can learn it. Our lives are also disrupted a lot. We are not allowed to gather. Not allowed to stand close to talk to each other, creating distance between people. Some of you, just sitting at home and watching Phones and computers, greatly affect your health. So let's fight against Covid 19 together

1 tháng 10 2021

Refer:

Hanoi is a dreamy city has been infatuated human heart. Besides the noise and busyness, that is the poetic and peaceful beauty. From long time ago, Hanoi was famous for thirty-six streets… Each street is a village, has unique characteristics unique. In general, people here are very elegant, open-minded and friendly. They are very willing to give directions to tourists and even invite them home. Besides, they are also very hardworking people, always try their best in life. Most of their time they spend on working and raising their children. Coming to Hanoi, we can not ignore the tourist attractions such as Bat Trang pottery village, the Temple of Literature, President Ho Chi Minh mausoleum, one pillar pagoda, ... They are associated with the existence and development of Hanoi, also Vietnam. Here, we will be attracted by the special dishes such as Vong Rice, Trang Tien ice cream, Ho Tay shrimp cake ... They are very delicious and are special characteristic of Hanoi, not similar to anywhere. For me, Hanoi is a beautiful and poetic city. Hope that one day, I will meet the dream of a travel to Bat Trang pottery.

26 tháng 10 2018

Each summer vacation, I am taken to the countryside by my parents so as to relax after a hard working term. I really like the life here. In rural areas, there are not as many houses and vehicles as in the city. As the result, the atmosphere is quite fresh and cool. Most people mainly travel by bicycle or on foot. The landscape is very poetic and picturesque. There are many gardens, rivers here. We can grow vegetables or chickens, fish,... on our own. The local are very kind, generous and friendly. They are willing to give directions to strangers and help each other in difficult times. Whenever we are away, we can relievedly ask our neighbors to keep our houses and children . Another thing that we especially like is that in the countryside, we are reconciled to nature so that the soul is always open and the body is healthy. Living in the countryside is fun and wonderful. In the future, I really want to live here.

30 tháng 10 2018

In the modern life, there is an increase in the people leave the countryside and migrate to the city. The objective reason is that in the city, it brings them comfortable life and favorite job. Subjective causes are due to the following disadvantages rural areas bring about push residents away. To begin with, there is no denial that rural infrastructure is not modern and advanced. Roads are quite narrow and degraded. Schools, hospitals are not cared much and remodeled. Especially the quality teachers and doctors here are just little so the inhabitants have less opportunity to develop in all way than in the urban area. Last but not least, the biggest disadvantage in rural areas is that job opportunities are so race. The main job is craft, farming, which bring a relatively small income. With that salary, we can only live through the day, not afford for services, shopping, entertainment… In conclusion, besides the positive aspects, life in the countryside is very much. disadvantage. We all need to consider carefully before choosing where to live.

Bài viết 1. Viết về lợi ích của việc học tiếng Anh bằng tiếng Anh:
Vocabulary:

  • Gradually (adv): Một cách từ từ.
  • Convincing (adj): Thuyết phục.
  • Demonstrating (adj) - demonstration (n): Minh họa
  • Scan (v): Quét (một kĩ năng chọn lọc thông tin cụ thể trong đọc).
  • Skim (v): Lướt (một kĩ năng lướt nhanh để lấy ý chính trong đọc).


I have been studying English since I was in secondary, and I realized that I had gain a lot of benefits from learning that language. First, English makes me become much more confident in communicating and expressing my opinion. Through pracing in speaking class, I can develop both my communicating and pronouncing skills. Second, English is a good supporting subject for my writing skill. By following the available grammars, I can gradually know how to make more convincing arguments as well as give demonstrating examples. Third, listening skill helps me to have more focus to the details in every conversation. In that way I can collect more valuable information in just a short time. Besides, I can also develop me note-taking skills since it is necessary to have a good note while I am listening to lectures. Last, what I had learnt in reading skill can be applied perfectly in reading any kind of material. By scanning and skimming, I can understand thoroughly the main ideas of each page. In sum up, all of the four skills of English can parularly help me in a lot of aspects. I am happy that I started learning English at a very young age, and I will continue to prace it.

Dịch:
Tôi bắt đầu học tiếng Anh từ khi tôi học cấp hai, và tôi nhận ra mình đã thu được rất nhiều lợi ích từ việc học ngôn ngữ đó. Đầu tiên, tiếng Anh khiến tôi trở nên tự tin hơn rất nhiều trong việc giao tiếp và phát biểu ý kiến của mình. Thông qua việc rèn luyện ở những buổi học nói, tôi có thể phát triển cả hai kĩ năng giao tiếp và phát âm. Thứ hai, tiếng Anh là một môn hỗ trợ rất tốt cho kĩ năng viết của tôi. Bằng cách theo sát các ngữ pháp có sẵn, tôi dần biết được cách làm thế nào để có lập luận thuyết phục hơn cũng như cho được các ví dụ minh họa. Thứ ba, kĩ năng nghe giúp tôi chú ý hơn vào các chi tiết trong mỗi cuộc hội thoại. Điều đó giúp tôi thu thập được nhiều thông tin chính trong một khoảng thời gian ngắn. Bên cạnh đó, tôi còn có thể phát triển kĩ năng ghi chú của mình vì việc có một ghi chú tốt trong quá trình nghe giảng là một việc cần thiết. Cuối cùng, những gì tôi học được từ kĩ năng đọc có thể được áp dụng hoàn hảo cho việc đọc bất kì một nguồn tài liệu nào. Bằng cách lướt và quét thông tin, tôi có thể hiểu được toàn bộ những ý chính của mỗi trang. Kết lại rằng tất cả bốn kĩ năng trong tiếng Anh đều có thể giúp tôi một cách cụ thể trong nhiều khía cạnh. Tôi vui vì mình đã học tiếng Anh kể từ khi còn nhỏ, và tôi sẽ tiếp tục rèn luyện nó nhiều hơn nữa. 

11 tháng 3 2019

Nowadays, English is an international language, and most young people are learning this language with the hope of being able to communicate with people on over the world. English has become a compulsory subject at most schools, and a lot of people go to foreign language teaching centers to improve their skills. Learning English is not just limited in memorizing vocabulary and grammar, but it is also a process of training and improving listening, speaking, reading, and writing skill. We should focus on these four elements, because each skill will have the necessary content to complement the other three. We improve our speaking skill if we can listen to and understand what people say; and if we can master our vocabulary and grammar, we can write and read easily. Apart from spending the time to prace, we also need to be creative in learning English. Textbooks at schools and English-teaching centers are just basic steps, so we need to be proactive in finding more resources. There are a lot of movies, music and books written in English nowadays, and we can learn a lot from them. In short, learning English is a long process, but it will be easier if we can find the right and effective ways to learn.