Gọi O là tâm hình bình hành ABCD. Đẳng thức nào sau đây sai?

A.  O A → − O B → = C D → .

B.  O B → − O C → = O D → − O A → .

C.  A B → − A D → = D B → .

D.  B C → − B A → = D C → − D A → .

Gọi z 1 , z 2  là các nghiệm phức thỏa mãn z 1 = z 2 = 1  và z 1 - 2 z 2 = 6 . Tính giá trị của biểu thức P = 2 z 1 + z 2 .

A. P = 2

B. P = 3

C. P = 3

D. P = 1

Đặt tính rồi tính:

34,56   +  19,45 

Cho hình vuông có đường chéo là 6( dm ) thì diện tích là ?

A. 24 c m 2  

B. 18 c m 2  

C. 21 c m 2    

D. 10 c m 2  

Read the following passage carefully, and then select the best option A, B, C or D to complete it

World Wide Web (WWW), computer-based (1) _______ of information resources that combines text and multimedia. The information on the World Wide Web can be accessed and searched through the (2) _______, a global computer network. The World Wide Web is often (3) _______ to simply as “the Web.”

The Web started to become a (4) _______ resource after 1993 when the first widely distributed browser provided a convenient way to (5) _______ a variety of information on the Internet. The Web uses (6) _______, which means that information can be displayed in a wide variety of formats. (7) _______ can read text, view pictures, watch animation, listen to sounds, and even explore interactive virtual environments on the Web. A user can (8) _______ seamlessly from a document or Web page stored on the computer to a document or Web page (9) _______ on another computer.

The Web offers a place where companies, universities and (10) _______ institutions, and individuals can display information about their products, services, facilities, or research, or their (11) _______ lives. Only a small percentage of information on the (12) _______ is restricted to subscribers or other authorized users. The majority of Web pages are available to (13) _______ who can access a computer that connects to the Internet. The Web has become a (14) _______ for many companies selling products or services, and a forum for people to exchange opinions and information. Museums, libraries, government agencies, and schools post information on the Web to make it (15) _______ to others.

Question 13:

A. no one

B. everyone

C. someone

D. anyone