Lập bảng biến thiên và vẽ đồ thị của hàm số bậc hai

y   =   - 3 x 2   -   6 x   +   4

\(2x^2-3x+2xy-3y\)

=2.x.x - 3.x + 2xy - 3y

=(2x-3).x + ( 2x-3)y

=(2x-3y).(x+y)

Một tụ điện phẳng có điện dung C, được mắc vào một nguồn điện, sau đó ngắt khỏi nguồn điện. Người ta nhúng hoàn toàn tụ điện vào chất điện môi có hằng số điện môi ε . Khi đó điện dung của tụ điện

A. Không thay đổi

B. Tăng lên  ε  lần

C. Giảm đi ε  lần

D. Tăng lên hoặc giảm đi tuỳ thuộc vào lớp điện môi

\(\dfrac{16}{11}\)

Mark the letter A, B, C, or D to indicate the correct answer to each of the following sentences.

My uncle is in _______ of 60 engineers and workers.

A. charge

B. management

C. leadership

D. direction

So sánh năng lượng liên kết của electron trong nguyên tử hidro và năng lượng liên kết của một proton trong hạt nhân 

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 following questions.

Becoming an Art Dealer

It is many peoples dream to become a world-famous artist. Unfortunately, it can be extremely difficult to make a living solely from selling your paintings or sculptures. But don’t worry because there are other jobs in the world of art that you can pursue. One possible career option is to become an art dealer.

An art dealer works on behalf of artists to help them sell works to museums and galleries around the world. To be successful at this profession, it requires a well-rounded skill set. For starters, it helps a lot if you love art and are knowledgeable about art history. Having business skills will also be quite useful, as it will be necessary to negotiate with buyers, and help the artists you represent market their work. If becoming an art dealer sounds appealing, there are several steps which you can follow. Although you may have a love for a wide range of styles, you should start by choosing one category to focus on. Buyers usually prefer to deal with a specialist in a particular area than someone who is a jack of all trades. When selecting your focus, choose an area that you are passionate about instead of something that seems lucrative. Art trends come and go, so there is no use trying to predict what is hot. These trends will certainly change over the course of your career. 

Once you selected an area to focus on, start to contact some museums, galleries, and other companies in the art world and send them your resume. The majority of art dealers begin their careers working as interns for these kinds of companies. Although these interns may be paid little, or in some cases nothing at all, the experience of learning how art businesses work will certainly serve you down the road.

It pays to be flexible in the beginning, as the most important thing is to get your foot in the door. Museums and galleries may offer you several positions including a sales assistant or a junior art consultant. Whichever job you accept, be sure to learn it well and give it your best. In addition to your responsibilities, make sure your start to network with others in your industry. As your knowledge and contacts begin to grow, more opportunities will be open to you.

What is the passage mainly about?

A. Suggestions about how to get a job in the art world 

B. The best-selling paintings in modern times

C. How to become a famous artist 

D. Some helpful art schools students should consider

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 35 to 42.

        Most desert animals will drink water if confronted with it, but many of them never have any opportunity. All living things must have water, or they will expire. The herbivores find it in desert plants. The carnivores slake their thirst with the flesh and blood of living prey. One of the most remarkable adjustments, however, has been made by the tiny kangaroo rat, who not only lives without drinking but subsists on a diet of dry seeds containing about 5% free water. Like other animals, he has the ability to manufacture water in his body by a metabolic conversion of carbohydrates. But he is notable for the parsimony with which he conserves his small supply by every possible means, expending only minuscule amounts in his excreta and through evaporation from his respiratory tract.

        Investigation into how the kangaroo rat can live without drinking water has involved various experiments with these small animals. Could kangaroo rats somehow store water in their bodies and slowly utilize these resources in the long periods when no free water is available from dew or rain? The simplest way to settle this question was to determine the total water content in the animals to see if it decreases as they are kept for long periods on a dry diet. If they slowly use up their water, the body should become increasingly dehydrated, and if they begin with a store of water, this should be evident from an initial high water content. Results of such experiments with kangaroo rats on dry diets for more than 7 weeks showed that the rats maintained their body weight. There was no trend toward a decrease in water content during the long period of water deprivation. When the kangaroo rats were given free access to water, they did not drink water. They did nibble on small pieces of watermelon, but this did not change appreciably the water itent in their bodies, which remained at 66.3 % to 67.2 % during this period.

          This is very close to the water content of dry-fed animals (66.5 %), and the availability of free water, therefore, did not lead to any “storage” that could be meaningful as a water reserve. This makes it reasonable to conclude that physiological storage of water is not a factor in the kangaroo rat’s ability to live on dry food.

The author states that the kangaroo rat is known for all of the following EXCEPT _________.

A. the economy with which it uses available water.

B. living without drinking water.

C. breathing slowly and infrequently.

D. manufacturing water internally.