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There is no denying that computer is one of the all-time greatest inventions of human being. It has brought us an endless number of benefits. This miraculous tool not only allows us to edit documents, to create excel worksheets or to install programs to serve our needs but also helps our kids relax with a wide range of games and apps. However, some people believe that computers may bring more harm than benefits if children use them daily; meanwhile, others state that they are helpful and can affect children positively. In my opinion, I totally agree with the first idea because of the following reasons.\nTo begin with, children will be isolated from other people around them if they use computers frequently. It’s simply because they spend most of their time on utilizing computers, so they do not have much communication with their parents. Moreover, when computers become their close friend, they may refuse to play with other kids as well as to take part in outdoor activities. It means there is less interaction between them and their fellows. Obviously, this is not recommended for children since they need to be active and to learn new things from family and friends to broaden their horizon. \nAnother point is that using computers uncontrollably may cause children to develop some diseases. Sitting in front of the computer regularly may lead to obesity because every day, children absorb a large amount of nutrition such as fat, protein and starch but they do not take exercises to consume this energy. Seriously, obesity can put them at higher risk of developing diabetes. Besides, some research has shown that looking at the computer screen continuously with concentration more than 2 hours will reduce our vision and cause myopia easily.\nThe last reason is that children can neglect their study and sink into computer games. It goes without saying that computer games are so addictive. If kids are unable to control themselves, they may spend all their time on playing games. After completing a level, they will have promotion to continue to play and to unlock new levels, then all these things will be repeated over and over again. In addition, computer games can inhibit the ability of thinking of children because they do not need to rack their brains a lot when playing games. Consequently, their study results may become worse and this will affect their future significantly.\nIn conclusion, I am totally in agreement with the idea that using computers daily will put great negative impacts on children. However, they can still take advantages of this wonderful invention if they use it suitably and effectively. Therefore, parents should teach their kids to be self-disciplined and to manage their time well when using computers.

Cho hình chóp S.ABCD có đáy ABCD là hình vuông cạnh a, cạnh bên SA vuông góc với đáy A B C D  và S C = a 5 . Tính thể tích khối chóp S.ABCD.

A. V = a 3 3 3 .

B. V = a 3 3 6 .

C. V = a 3 3 .

D. V = a 3 15 3 .

Điền số thích hợp vào chỗ chấm:

a) 24573 dm = ………………..km

b) 13 k m 2 45 d a m 2 = ……………….. d a m 2

Cho hàm số  y = 3 x - 1 - 4 + 2 x  Khẳng định nào sau đây là khẳng định đúng?

A. Hàm số nghịch biến trên R

B. Hàm số luôn nghịch biến trên từng khoảng xác định.

C. Hàm số đồng biến trên các khoảng - ∞ ; 2   v à   2 ; + ∞

D. Hàm số nghịch biến trên các khoảng - ∞ ; - 2   v à   2 ; + ∞

Với giá trị nào của m thì hàm số y = (2 – 3m)x + 5m là hàm số nghịch biến?

A.  m > 2 3

B.  m > - 2 3

C.  m < 2 3

D.  m < - 2 3

Cho hàm số bậc nhất y=(m+1)x+5

a) Tìm giá trị của m để hàm số trên là đồng biến, nghịch biến

Hãy viết những điều đã kể ở bài tập 1 thành một đoạn văn.