Cho cấp số cộng \(\left(u_{n}\right)\) có \(u_{1}=4\). Giá trị nhỏ nhất của \(u_{1} u_{2}+u_{2} u_{3}+u_{3} u_{1}\) bẳng:
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Ta gọi \(d\) là công sai của cấp số cộng.
Khi đó:
\(u_{1} u_{2}+u_{2} u_{3}+u_{3} u_{1}=4(4+d)+(4+d)(4+2 d)+4(4+2 d)\)
\(=2 d^{2}+24 d+48=2(d+6)^{2}-24 \geq-24\)
Vậy giá trị nhỏ nhất của \(u_{1} u_{2}+u_{2} u_{3}+u_{3} u_{1}\) là -24 đạt được khi khi \(d=-6\).
Đề Thi Tham Khảo Đánh Giá Năng Lực Năm 2024 – ĐHQG Hà Nội – Đề Số 01 là bài kiểm tra toàn diện và khoa học, giúp học sinh thể hiện năng lực giải quyết vấn đề, tư duy sáng tạo và phân tích logic. Với ba phần thi chính: Toán Học Và Xử Lí Số Liệu, Văn Học - Ngôn Ngữ, và Khoa Học/Tiếng Anh, đề thi không chỉ dừng lại ở việc kiểm tra kiến thức cơ bản mà còn yêu cầu thí sinh phát triển khả năng lập luận và ứng dụng thực tiễn. Đặc biệt, phần thi Khoa Học cho phép lựa chọn giữa Vật Lí, Hóa Học, Sinh Học, Lịch Sử, Địa Lí tạo điều kiện cho thí sinh phát huy thế mạnh cá nhân.
Câu hỏi liên quan
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.
Dear Anna,
a. I’m grateful for the advice you gave me about the project; it was really helpful.
b. I’ll keep you updated on my progress and let you know how things go.
c. I’ve made significant improvements thanks to your suggestions.
d. Let’s catch up over coffee sometime next week if you’re free.
e. Thanks again for always being supportive.
Best regards,
Emily
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Read the passage and mark the letter A, B, C or D to answer the following questions.
Volunteering offers many of the same social benefits, with the added bonus of helping others and developing useful skills to put on your CV. Plus, students are in a unique position to help, suggests Tom Fox. "They can take their enthusiasm and excitement for opportunities and share their passions, subject knowledge and experience with people." The idea of giving up time for nothing might seem impractical at first, especially once the pressures of study and coursework or exams begin to mount up. However, Michelle Wright, CEO of charity support organization Cause4, suggests seeing volunteering as a two-way street. "I think it is fine for undergraduates to approach volunteering as a symbiotic relationship where doing good is just one part of the motivation for reaching personal and professional goals."
Katerina Rudiger, head of skills and policy campaigns at the Chartered Institute of Personnel and Development (CIPD), says: "Volunteering can be a valuable way of gaining that experience, as well as building confidence, broadening your horizons, becoming a better team player and developing those all- important 'employability skills' such as communication and decision making." Amanda Haig, graduate HR manager, agrees that volunteering can help your employment prospects. "Volunteering can demonstrate positive personality traits and skill sets, such as proactivity, and teamwork," she says.
A positive side-effect of volunteering is improving your time at university by getting involved in the local community. Leaving the student bubble can make your time as an undergraduate much more varied. At Bath Spa University, more than 1,000 students volunteered over the past year, doing everything from working on local environmental projects to helping in schools or assisting the elderly. ”Quite often there can be a divide between students and permanent residents," says students' union president Amy Dawson, "but if students invest a little time now, they will be giving something back to the local community and will reap the benefits in the future."
“You might also find that volunteering helps your studies if you choose the right program. At Lancaster, volunteering is linked into academic modules in some cases", explains Fox. "This has multiple wins. Students get to apply their learning in the classroom and share their interests with children in local schools or community organizations, while schools gain skilled students with a passion for a subject that enthuses their pupils."Personality traits and skill sets include____________.
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Read the following notice about a new travel platform 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 1 to 6
MAKING HONEY
Do you like honey? Honey is a natural product, and it is made by honey bees. It has (1) __________ , which some people prefer to ordinary sugar. Sometimes it’s possible to know (2) __________ the flavour what kind of flowers the bees visited before producing the honey. Have you ever (3) __________ about how honey is produced? Beekeepers – people who look after bees are very important in the making of honey. They let the bees in their care (4) __________more honey than is needed. Then the honey can be removed without causing problems for the bees. Honey collection is an ancient activity, (5) __________ back at least 10.000 years. Thus, honey has become increasingly (6) __________ nowadays as a healthy food, so people of all age can use it not only to treat some simple ailments but also to slow down aging process.
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. Để có thể xảy ra hiện tượng cộng hưởng, người ta thực hiện phương án nào sau đây?
Nhu cầu sử dụng dịch vụ lưu trữ trực tuyến gia tăng vì thiết bị thông minh thường
Read the following passage about endangered languages and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questionsfrom 31 to 40.
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Despite these advantages, there are serious concerns about the negative impact of social media, particularly on mental health. Studies have shown that excessive social media use can contribute to feelings of anxiety, depression, and loneliness. This is often attributed to the unrealistic portrayals of life that are commonly shared on these platforms, leading to comparisons that can make individuals feel inadequate or left out. Furthermore, constant exposure to negative news or online bullying can exacerbate these feelings and contribute to long-term psychological stress.
Another issue with social media is its potential to distract people from their daily responsibilities. With notifications constantly popping up and endless streams of content to scroll through, individuals may find it difficult to focus on tasks such as work, school, or personal obligations. This can result in decreased productivity and a lack of attention to important matters.
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Ý nào không phản ánh ý nghĩa của cuộc cách mạng Tân Hợi?
Thông tin của thị trường quan trọng như thế nào đối với người bán?
Thị trường thừa nhận công dụng xã hội của hàng hoá và lao động đã hao phí để sản xuất ra nó, thông qua việc hàng hoá có bán được hay không và bán với giá như thế nào thể hiện
Trên mặt phẳng tọa độ Oxy, tiếp tuyến của đồ thị hàm số \(y={{x}^{3}}+3{{x}^{2}}-6x+1\) tại điểm có hoành độ bẳng 1 và cắt hai trục tọa độ tại A, B. Tính diện tích tam giác OAB.
(nhập đáp án vào ô trống, kết quả làm tròn đến chữ số thập phân thứ hai).