Cho tập hợp E = {x ∈ ℕ | x là ước chung của 20 và 40}.

Tập hợp E có bao nhiêu phần tử?

Dãy nào sau đây gồm các đồng vị của cùng một nguyên tố hoá học?

Ngoc _______ in the kitchen when she saw a mouse.

Cho tập hợp $M = \{(x; y)\, \big| \,x$, $y \in \mathbb{R}$, $x^2 + y^2 \le 0\}$. Khi đó tập hợp $M$ có bao nhiêu phần tử?

Mark the letter A, B, C, or D on your answer sheet to indicate the best arrangement of utterances or sentences to make a meaningful exchange or text in each of the following questions.

a. Tina: That sounds interesting! I think I’ll join too. Do you know when the sign-up period ends?

b. Sarah: Yes, I heard they offer various sports like soccer, basketball, and swimming.

c. Tina: Hi Sarah, are you going to join the new sports club at school?

d. Tina: Good idea! Let’s meet after school tomorrow and sign up together.

e. Sarah: I believe it ends next Friday. We should sign up as soon as possible to secure our spots.

Cho đoạn chương trình sau:

a=4

x=math.sqrt(a)

Sau khi thực hiện đoạn chương trình trên giá trị của x là:

Trong quang hợp, pha sáng cung cấp cho pha tối chất gì?

Biết $\overrightarrow{d_1}$ là độ dịch chuyển 5 m về phía Nam, $\overrightarrow{d}_2$ là độ dịch chuyển 8 m về phía Bắc. Độ dịch chuyển tổng hợp $\overrightarrow{d}$ có

Read the passage carefully. Choose an option (A, B, C, or D) that best answers each question from to 646 to 650:

1. Millions of people are using cellphones today. In many places, it is actually considered unusual not to use one. In many countries, cellphones are very popular with young people. They find that the phones are more than a means of communication - having a mobile phone shows that they are cool and connected.

2. The explosion in mobile phone use around the world has made some health professionals worried. Some doctors are concerned that in the future many people may suffer health problems from the use of mobile phones. In England, there has been a serious debate about this issue. Mobile phone companies are worried about the negative publicity of such ideas. They say that there is no proof that mobile phones are bad for your health.

3. On the other hand, medical studies have shown changes in the brain cells of some people who use mobile phones. Signs of change in the tissues of the brain and head can be detected with modern scanning equipment. In one case, a traveling salesman had to retire at young age because of serious memory loss. He couldn't remember even simple tasks. He would often forget the name of his own son. This man used to talk on his mobile phone for about six hours a day, every day of his working week, for a couple of years. His family doctor blamed his mobile phone use, but his employer's doctor didn't  agree.

4. What is it that makes mobile phones potentially harmful? The answer is radiation. High-tech machines can detect very small amounts of radiation from mobile phones. Mobile phone companies agree that there is some radiation, but they say the amount is too small to worry about.

5. As the discussion about their safety continues, it appears that it's best to use mobile phones less often. Use your regular phone if you want to talk for a long time. Use your mobile phone only when you really need it. Mobile phones can be very useful and convenient, especially in emergencies. In the future, mobile phones may have a warning label that says they are bad for your health. So for now, it's wise not to use your mobile phone too often.

What does the word “they” in paragraph 2 refer to?

Con lắc lò xo nằm ngang dao động điều hòa, vận tốc của vật bằng không khi vật chuyển động qua

Read the following passage about effective English language learning and mark the letter A, B, C or D on your answer sheet to indicate the option that best fits each of the numbered blanks from from 18 to 22.

Learning a new language, especially English, can be both challenging and rewarding. To maximize your language learning potential, it's essential to adopt effective strategies. ___(18)___. By understanding your learning style and setting clear goals, you can create a personalized learning plan.

One of the most effective ways to improve your English is through consistent practice. ___(19)___. This could involve reading books, articles, or news, watching movies or TV shows, or listening to English songs or podcasts.

To enhance your speaking skills, it's crucial to engage in regular conversation practice. ___(20)___. Joining language exchange groups or finding a language partner can provide opportunities to practice speaking and receive feedback.

While practice is essential, it's equally important to learn correct grammar and vocabulary. ___(21)___. Using grammar books, online resources, or language apps can help you master the rules of English grammar.

In conclusion, effective English language learning requires a combination of consistent practice, strategic learning, and a positive mindset. ___(22)___. By embracing these strategies, you can achieve your English language goals and open up new opportunities.

Chọn ngẫu nhiên lần lượt các số \(a, b\) phân biệt thuộc tập hợp \(\left\{3^{k} \mid k \in \mathbb {N}, 1 \leq k \leq 10\right\}\). Tính xác suất để \(\log _{a} b\) là một số nguyên dương.

Cho HS \(f(x) = \left\{ \begin{array}{l}\sqrt {x + 1} - 2\quad (x \ge - 1)\\3{x^2} - x + 1\quad (x < - 1)\end{array} \right.\). Tính giá trị của \(2.f( - 3) - 4.f(0)\)?

Đâu là các đồng bằng ở miền Đông Trung Quốc theo thứ tự từ Bắc xuống Nam?

Một người có thể bơi với vận tốc 2,5 m/s khi nước sông không chảy. Khi nước sông chảy với vận tốc 1,2 m/s theo hướng bắc nam thì sẽ làm thay đổi vận tốc của người bơi. Tìm vận tốc tổng hợp của người đó khi bơi ngược dòng chảy.

Thủ pháp nghệ thuật đặc sắc trong hai câu cuối bài thơ Thu điếu?

The situation looks_______. We must do something.

Phương án nào dưới đây thuộc thị trường các loại hàng hoá và dịch vụ?