Cho $A=\{x\in \mathbb{N}|\left(2x–x^2\right)\left(2x^2–3x–2\right)=0\}$ và $B=\{n\in \mathbb{N}*|3<n^2<30\}$. Tìm kết quả phép toán $A\cap B$.

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:

Ambient divers are, unlike divers who go underwater in submersible vehicles of pressure resistant suits, exposed to the pressure and temperature of the surrounding ambient water. Of all types of diving, the oldest and simplest is free diving. Free divers may use no equipment at all, but most use a face mask, foot fins, and a snorkel. Under the surface, free divers must hold their breath. Most free divers can only descend 30 to 40 feet, but some skilled divers can go as deep as 100 feet.

Scuba diving provides greater range than free diving. The word scuba stands for self-contained underwater breathing apparatus. Scuba divers wear metal tanks with compressed air or other breathing gases. When using open-circuit equipment, a scuba diver simply breathes air form the tank through a hose and releases the exhaled air into the water. A closed-circuit breathing device, also called a rebreather, filters out carbon dioxide and other harmful gases and automatically adds oxygen. This enables the diver to breathe the same air over and over. In surface-supplied diving, divers wear helmets and waterproof canvas suits. Today, sophiticated plastic helmets have replaced the heavy copper helmets used in the past. These divers get their air from a hose connected to compressors on a boat. Surface-supplied divers can go deeper than any other type of ambient diver.  

Question: What does the word “descend” in the paragraph probably mean?         

Khi nói về dao động cơ cưỡng bức, phát biểu nào sau đây là sai?

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:

Ambient divers are, unlike divers who go underwater in submersible vehicles of pressure resistant suits, exposed to the pressure and temperature of the surrounding ambient water. Of all types of diving, the oldest and simplest is free diving. Free divers may use no equipment at all, but most use a face mask, foot fins, and a snorkel. Under the surface, free divers must hold their breath. Most free divers can only descend 30 to 40 feet, but some skilled divers can go as deep as 100 feet.

Scuba diving provides greater range than free diving. The word scuba stands for self-contained underwater breathing apparatus. Scuba divers wear metal tanks with compressed air or other breathing gases. When using open-circuit equipment, a scuba diver simply breathes air form the tank through a hose and releases the exhaled air into the water. A closed-circuit breathing device, also called a rebreather, filters out carbon dioxide and other harmful gases and automatically adds oxygen. This enables the diver to breathe the same air over and over. In surface-supplied diving, divers wear helmets and waterproof canvas suits. Today, sophiticated plastic helmets have replaced the heavy copper helmets used in the past. These divers get their air from a hose connected to compressors on a boat. Surface-supplied divers can go deeper than any other type of ambient diver.  

 Question: When using closed-circuit devices, divers_______.          

Dao động tắt dần:

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:

Ambient divers are, unlike divers who go underwater in submersible vehicles of pressure resistant suits, exposed to the pressure and temperature of the surrounding ambient water. Of all types of diving, the oldest and simplest is free diving. Free divers may use no equipment at all, but most use a face mask, foot fins, and a snorkel. Under the surface, free divers must hold their breath. Most free divers can only descend 30 to 40 feet, but some skilled divers can go as deep as 100 feet.

Scuba diving provides greater range than free diving. The word scuba stands for self-contained underwater breathing apparatus. Scuba divers wear metal tanks with compressed air or other breathing gases. When using open-circuit equipment, a scuba diver simply breathes air form the tank through a hose and releases the exhaled air into the water. A closed-circuit breathing device, also called a rebreather, filters out carbon dioxide and other harmful gases and automatically adds oxygen. This enables the diver to breathe the same air over and over. In surface-supplied diving, divers wear helmets and waterproof canvas suits. Today, sophiticated plastic helmets have replaced the heavy copper helmets used in the past. These divers get their air from a hose connected to compressors on a boat. Surface-supplied divers can go deeper than any other type of ambient diver.  

Question: Ambient divers are ones who_____.             

Một vật nhỏ có khối lượng 500 g dao động điều hòa dưới tác dụng của một lực kéo về có biểu thức N (t đo bằng s). Dao động của vật có biên độ là ?  

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions

He wanted to know _______.         

Hiện tượng cộng hưởng thể hiện rõ nét nhất kh ?  

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 from 43 to 50:

Smallpox was the first widespread disease to be eliminated by human intervention. Known as a highly contagious viral disease, it broke out in Europe, causing the deaths of millions of people until the vaccination was invented by Edward Jenner around 1800. In many nations, it was a terror, a fatal disease until very recently. Its victims suffer high fever, vomiting and painful, itchy, pustules that left scars. In villages and cities all over the world, people were worried about suffering smallpox.In May, 1966, the World Health Organization (WHO), an agency of the United Nations was authorized to initiate a global campaign to eradicate smallpox. The goal was to eliminate the disease in one decade. At the time, the disease posed a serious threat to people in more than thirty nations. Because similar projects for malaria and yellow fever had failed, few believed that smallpox could actually be eradicated but eleven years after the initial organization of the campaign, no cases were reported in the field.The strategy was not only to provide mass vaccinations but also to isolate patients with active smallpox in order to contain the spread of the disease and to break the chain of human transmission. Rewards for reporting smallpox assisted in motivating the public to aid health workers. One by one, each small-pox victim was sought out, removed from contact with others and treated. At the same time, the entire village where the victim had lived was vaccinated.By April of 1978 WHO officials announced that they had isolated the last known case of the disease but health workers continued to search for new cases for additional years to be completely sure. In May, 1980, a formal statement was made to the global community. Today smallpox is no longer a threat to humanity. Routine vaccinations have been stopped worldwide.  

Question 49: Which one of the statements doesn’t refer to smallpox?         

Một con lắc lò xo treo thẳng đứng, trong đó vật nặng được làm bằng kim loại. Tại vị trí cân bằng, lò xo dẫn một đoạn 1cm. Đặt dưới vật nặng một nam châm điện được duy trì hoạt động bằng một dòng điện xoay chiều. Biết rằng trong một chu kì của dòng điện có hai lần lực tác dụng lên hệ. Lấy . Để vật nặng dao động với biên độ mạnh nhất thì tần số của dòng điện là ?