Bài tập: Rút gọn biểu thức.

\(3\sqrt{x-1}+2\sqrt{4x-4}-3\sqrt{9x-9}+6=0\)

Một trường Tiểu học có 555 học sinh. Số học sinh trai nhiều hơn số học sinh gái 27 em. Hỏi trường Tiểu học đó có bao nhiêu học sinh trai, bao nhiêu học sinh gái?

Technological advances have spawned the foundations of computers and the internet, and they have also spurred the opposite to create a change in the world today. Interactive interactions in new technologies have led to dramatic changes in the lives of people today. We no longer have to write handwritten messages to distant relatives, or access to information not only from articles or magazines published on paper ... and clearly on All these are commercial activities through cyberspace including e-commerce.

More and more of our activities are closely linked to scientific and technical innovations. Even areas that have traditionally been understood as "remote" activities to urban life like agriculture have also been significantly affected since the development of IT. For example, in the past, agricultural production from seed selection, tillage, to harvesting was a far cry from the consumer. Today, with the update of the farming process and more about the farming method to create a product of sufficient quality and reputation for consumers through the website, the brand with full bar codes and identification marks.

Chứng minh rằng a b c d ¯ ⋮ 29 ⇔ a + 3 b + 9 c + 27 d ⋮ 29

Environment is an essential part of our life. A clean environment is necessary for a peaceful and healthy life. An environment is the natural surroundings which helps human beings, animals and other living things to grow and develop naturally. But nowadays, our environment is disturbing in many different ways. Any type of disturbance in the nature’s balance affects the environment totally. It does not only ruin human lives but also affects on all living beings. We can save our environment with the little step taken by everyone on the earth. We should reduce the amount of waste, throwing wastes properly to its place only…and many other simple ways. It is very important to save environment for human existence. When we protect the environment, we are protecting ourselves and our future as well.

You can reduce the amount of waste you create by choosing what rubbish you throw away. This can be easy and fun – just follow our simple guidelines to reduce your waste at home, school or work.

Waste reduction starts at the supermarket. By making slight alterations to your shopping list you can significantly reduce the amount of waste created in and around the home.

Buy only what you need

Reduce unnecessary waste by avoiding those pointless purchases. Items that rarely get used can be borrowed or shared with others.

Buy products that can be reused

Buy bottles instead of cans and rechargeable batteries. Items such as this create very little waste, as they don’t have to be thrown away after they have been used just once.

Buy all-purpose household cleaner

Instead of buying many different ones for each cleaning role.

Buy products with little packaging

So that less packaging ends up in your rubbish bin. For those items you use regularly, buy them in bulk instead of in smaller amounts. This will save you money as well as reduce waste.

Sell or give away unwanted items Reduce waste by donating unwanted items to family, friends or neighbours. You could even sell your possessions in a car-boot sale and earn some extra cash.

Reduce paper waste by cancelling unwanted mail You can unsubscribe to many national mailing lists by contacting the Direct Marketing Association:

www.dma.org.uk

Many hazardous products cannot be recycled as they contain harmful chemicals. However, there are ways of reducing waste by dealing with hazardous products in the correct manor.

Buy non-toxic products whenever possible

Many toxic products such as motor oil and pesticides cannot be reused.

Recycle motor products

Such as break fluid, oils and tyres by taking them to your local petrol station. By recycling these products instead of throwing them away, you are reducing hazardous waste.

Use all of the toxic product, such as furniture polish, so there is no hazardous material left in the container when it is discarded.

Find safer alternatives to hazardous household products.

You can even make your own household cleaners using products such as baking soda and vinegar. Olive oil with lemon juice is a good alternative to furniture polish and using scented candles are a good alternative to air fresheners.

Life in the city, compared with life in the country

In my opinion, urban life or rural life has its own advantages and disadvantages.
First, living in the city we may enjoy those benefits.
- Communication and transportation systems are better. There are so many means of communication and transport that we can choose the ones we like best. We can get in touch with a friend or talk to him by phone without having to go out of home.
- Thanks to electricity network and running water, our material lives are more comfortable. Supermarkets, markets and shops are found everywhere and we can buy anything we need providing that we can afford it.
- Urban life provides us with all sorts of entertainments: televisions, radios, movies, theatres, concerts and famous recreation centers.
- Living in town we can improve our knowledge easily by attending any schools, universities or evening classes where experienced teachers and professors are ready to satisfy our thirst for knowledge.
Besides its advantages, urban life also has its disadvantages:
- Our health is in danger: pollution by factories and heavy traffic may cause serious diseases to all of us.
- Evil influence upon the young generation by obscene video films is inevitable.
- Violent deaths happen regularly in such a crowded city with all kinds of vehicles.
On the contrary, rural life seems ideal to all of us, especially to the old.
- We can enjoy fresh, cool air and behold beautiful landscapes in the country.
- How safe and delighted we are when we can sleep a sound sleep at any time of the day without being disturbed by sirens of cars or by deafening noises from manufacturing factories.
- Our social lives in the country are easier: we can eat the food and vegetables we grow, the chickens and goats we raise. The countrymen lead a very simple life and they are quick at mutual Giúp in any case.
Apart from these advantages, living in the country we may meet lots of difficulties too.
- Communication and transportation are obstructed by lack of means of transport or by floods in the rainy season.
- Our knowledge is limited by being short of mass media.
- Our social and physical lives are not as comfortable as those in town because of lack of electricity and medical care.
In a nutshell, our love for town life or country life depends on our outlook and age. As for me, I always prefer rural life to urban life.

Tìm x biết  x ⋮ 9 ,   22 ⩽ x ⩽ 28

A. x=22

B. x=25

C. x=27

D. Đáp án khác

Có bao nhiêu số tự nhiên có bốn chữ số khác nhau trong đó có đúng một chữ số 3?