Cho điểm H(4;0) đường thẳng x = 4  cắt hai đồ thị hàm số y = log a x và y = log b x lần lượt tại 2 điểm A, B sao cho A B = 2 B H . Khẳng định nào sau đây là đúng?

A.  b = a 3                      

B.  a = b 3  

C.  a = 3 b                    

D.  b = 3 a  

Read the passage carefully and choose the correct answers

Traveling is one of the most popular forms of recreation in the USA. Most American employees receive an annual vacation with pay, and it is a good time off for traveling. Traveling within the country is popular because foreign travel generally takes more time and money. However, Americans who wish to vacation outside the USA are free to go almost anywhere. Obtaining a passport is a routine matter. Every year about 13 million Americans travel abroad. The most popular vacation periods are during the summer and during the two-week school break on the Christmas and New Year’s holidays. These periods are also the most crowded and generally the most expensive time to travel, so people who can adjust their schedules sometimes choose vacation in the autumn. American vacationers often travel by car. Most families have a car, and those who do not have a car can rent one. Cars are usually the economical way to travel, especially for the families. It is also fairly fast and convenient. Excellent highways connect the major cities. They enable vacationers to travel at an almost steady speed of 55 to 65 miles an hour. Tourists that want to travel faster often fly to their destination and then rent a car to go around when they get there.

Question: Which sentence is NOT correct?

A. Most Americans like traveling.

B. Most American people travel abroad every year.

C. There is a two-week break on the Christmas and the New Year’s holidays.

D. It is difficult to obtain a passport in the USA.

Điền số thích hợp vào chỗ trống. Điểm T là trung điểm của đoạn thẳng AB.

Tìm m để hàm số:

y = 1 3 x 3 − m + 1 x 2 + m − 2 x + 2 m − 3 đạt cực trị tại 2 điểm x 1 , x 2 thỏa mãn x 1 2 + x 2 2 = 18  

A. m = − 5

B.  m = 1 m = − 5

C.  m = 1

D. m = 1 m = − 5 2

John had agreed ......................... me in his office.

A. to meet

B. meeting

C. to be met

D. being met

The doctor told him not to talk during the meditation.

A. He has been told by the doctor not to talk during the meditation.

B. He was told by the doctor not to talk during the meditation.

C. He is told by the doctor not to talk during the meditation.

D. He was being told by the doctor not to talk during the meditation.