Tìm đạo hàm của các hàm số sau  y   =   m   +   n x 2 3 (m, n là các hằng số)

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions. 

People travel for a lot of reasons: Some tourists go to see battlefields or religious shrines. Others are looking for culture, or simply want to have their pictures taken in front of famous places. But most European tourists are looking for a sunny beach to lie on. 

Northern Europeans are willing to pay a lot of money and put up with a lot of inconveniences for the sun because they have so little of it. Residents of cities like London, Copenhagen, and Amsterdam spend a tot of their winter in the dark because the days are so short, and much of the rest of the year in the rain. This is the reason why the Mediterranean has always attracted them. Every summer, more than 25 million people travel to Mediterranean resorts and beaches for their vacation. They all come for the same reason, sun!

The huge crowds mean lots of money for the economies of Mediterranean countries. Italy’s 30,000 hotels are booked solid every summer. And 13 million people camp out on French beaches, parks and roadsides. Spain’s long sandy coastline attracts more people than anywhere else. 37 million tourists visit yearly, or one tourist for every person living in Spain.

But there are signs that the area is getting more tourists than it can handle. The Mediterranean is already one of the most polluted seas on earth. And with increased tourism, it’s getting worse. The French can’t figure out what to do with all the garbage left by campers around St. Tropez. And in many places, swimming is dangerous because of pollution. 

          None of this, however, is spoiling anyone’s fun. The Mediterranean gets more popular every year with tourists. Obviously, they don’t go there for clean water and solitude. They tolerate traffic jams and seem to like crowded beaches. They don’t even mind the pollution. No matter how dirty the water is, the coastline still looks beautiful. And as long as the sun shines, it’s still better than sitting in the cold rain in Berlin, London, or Oslo.

The writer seems to imply that Europeans travel mostly for the reason that ______.

A. they want to see historic remains or religious spots.

B. they would like to take pictures in front of famous sites

C. they wish to escape from the cold, dark and rainy days back at home.

D. they are interested in different cultural traditions and social customs.

Một người nâng một tấm gỗ dài 1,5 m, nặng 30 kg và giữ cho nó hợp với mặt đất nằm ngang một góc 60^o. Biết trọng tâm của tấm gỗ cách đầu mà người đó nâng 120 cm, lực nâng vuông góc với tấm gỗ. Tính lực nâng của người đó.

A. 300 N                 

B. 51,96 N              

C. 240 N                  

D. 30 N

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions

Before the 1500’s, the western plains of North America were dominated by farmers. One group, the Mandans, lived in the upper Missouri River country, primarily in present – day North Dakota. They had large villages of houses built close together. The tight arrangement enabled the Mandans to protect themselves more easily from the attacks of others who might seek to obtain some of the food these highly capable farmers stored from one year to the next.

The women had primary responsibility for the fields. They had to exercise considerable skill to produce the desired results, for their northern location meant fleeting growing seasons. Winter often lingered; autumn could be ushered in by severe frost. For good measure, during the spring and summer, drought, heat, hail, grasshoppers, and other frustrations might await the wary grower.

Under such conditions, Mandan women had to grow maize capable of weathering adversity. They began as early as it appeared feasible to do so in the spring, clearing the land, using fire to clear stubble from the fields and then planting. From this point until the first green corn could be harvested, the crop required labor and vigilance.

Harvesting proceeded in two stages. In August the Mandans picked a smaller amount of the crop before it had matured fully. This green corn was boiled, dried and shelled, with some of the maize slated for immediate consumption and the rest stored in animal – skin bags. Later in the fall, the people picked the rest of the corn. They saved the best of the harvest for seeds or for trade, with the remainder eaten right away or stored for alter use in underground reserves. With appropriate banking of the extra food, the Mandans protected themselves against the disaster of crop failure and accompany hunger.

The woman planted another staple, squash, about the first of June, and harvested it near the time of the green corn harvest. After they picked it, they sliced it, dried it, and strung the slices before they stored them. Once again, they saved the seeds from the best of the year’s crop. The Mandans also grew sunflowers and tobacco; the latter was the particular task of the older men.

What is the main topic of the passage ?

A. The agricultural activities of a North American Society

B. Various ways corn can be used

C. The problems encountered by farmers specializing in growing once crop

D. Weather conditions on the western plains