Mệnh đề nào dưới đây có mệnh đề phủ định của nó là đúng?
Mệnh đề nào dưới đây có mệnh đề phủ định của nó là đúng?
A. "∀x ∈ ℝ: x < x + 2";
B. "∀n ∈ ℕ: 3n ≥ n";
C. "∃x ∈ ℚ: x2 = 5";
D. "∃x ∈ ℝ: x2 – 3 = 2x".
Hãy suy nghĩ và trả lời câu hỏi trước khi xem đáp án
- A. Mệnh đề $\forall x \in \mathbb{R}: x < x + 2$ luôn đúng, vì vậy mệnh đề phủ định của nó sai.
- B. Mệnh đề $\forall n \in \mathbb{N}: 3n \geq n$ luôn đúng, vì vậy mệnh đề phủ định của nó sai.
- C. Mệnh đề $\exists x \in \mathbb{Z}: x^2 = 5$ sai, vì không có số nguyên nào mà bình phương bằng 5. Phủ định của nó là đúng.
- D. Mệnh đề $\exists x \in \mathbb{R}: x^2 – 3 = 2x$ đúng, vì có nghiệm $x = 1 + \sqrt{4} = 3$. Vì vậy mệnh đề phủ định của nó sai.
Câu hỏi liên quan
Cơ sở khoa học của công nghệ tế bào dựa trên đặc tính nào sau đây của tế bào?
Năm 1915, Đức – Áo – Hung tập trung tấn công nước nào?
Read the following passage about powering and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questions from 31 to 40.
TikTok is a popular social media app where people can create and share short videos [I]. It started in China in 2016 as Douyin [II]. The app is known for its easy-to-use tools that let users add music, effects, and filters to their videos [III]. People of all ages enjoy making and watching TikTok videos, which can be funny, educational, or creative [IV].
One of the reasons TikTok is so popular is because of its algorithm, which shows users videos that match their interests. When you open the app, you see a personalized feed called the "For You" page. This page is different for everyone and updates with new videos all the time. Users can also follow their favorite creators to see more of their content.
TikTok has become a platform for trends and challenges. Many users participate in dance challenges, lip-syncing, and other viral activities. These trends can spread quickly, reaching millions of people in a short time. Because of this, TikTok has influenced music charts, fashion, and even language. Songs that go viral on TikTok often become hits on other platforms too.
The app is also a space for education and advocacy. Many creators use TikTok to share knowledge about various topics, such as science, history, cooking, and fitness. Others use the platform to raise awareness about social issues and promote positive change.
In addition to individual creators, many brands and businesses use TikTok for marketing. They create content to engage with their audience, often using popular trends and challenges to promote their products.
However, TikTok has faced some criticism and challenges. Concerns about privacy and data security have led to scrutiny from governments. Despite these issues, TikTok still remains one of the most downloaded apps in the world.
According to paragraph 2, which of the following is NOT true about TikTok's algorithm?
Cho tập X={0;1;2;3;4;5} và tập A={0;2;4}. Phần bù của A trong X là
Người ta trồng \(3\,003\) cây theo dạng một hình tam giác như sau: hàng thứ nhất trồng \(1\) cây, hàng thứ hai trồng \(2\) cây, hàng thứ ba trồng \(3\) cây, …, cứ tiếp tục trồng như thế cho đến khi hết số cây. Số hàng cây được trồng là bao nhiêu?
Read the following passage about powering and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questions from 31 to 40.
TikTok is a popular social media app where people can create and share short videos [I]. It started in China in 2016 as Douyin [II]. The app is known for its easy-to-use tools that let users add music, effects, and filters to their videos [III]. People of all ages enjoy making and watching TikTok videos, which can be funny, educational, or creative [IV].
One of the reasons TikTok is so popular is because of its algorithm, which shows users videos that match their interests. When you open the app, you see a personalized feed called the "For You" page. This page is different for everyone and updates with new videos all the time. Users can also follow their favorite creators to see more of their content.
TikTok has become a platform for trends and challenges. Many users participate in dance challenges, lip-syncing, and other viral activities. These trends can spread quickly, reaching millions of people in a short time. Because of this, TikTok has influenced music charts, fashion, and even language. Songs that go viral on TikTok often become hits on other platforms too.
The app is also a space for education and advocacy. Many creators use TikTok to share knowledge about various topics, such as science, history, cooking, and fitness. Others use the platform to raise awareness about social issues and promote positive change.
In addition to individual creators, many brands and businesses use TikTok for marketing. They create content to engage with their audience, often using popular trends and challenges to promote their products.
However, TikTok has faced some criticism and challenges. Concerns about privacy and data security have led to scrutiny from governments. Despite these issues, TikTok still remains one of the most downloaded apps in the world.
Which of the following best paraphrases the underlined sentence in paragraph 4?
Vì sao nói đến thời kì Hi Lạp và Rô-ma, các hiểu biết khoa học mới thực sự trở thành khoa học?
Read the following advertisement 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.
"Welcome to FitLife Gym, the newest fitness center in town! We take pride in offering you a modern space equipped with state-of-the-art equipment and a team of expert trainers (1)______ to helping you achieve your fitness goals. At FitLife, we provide a variety of programs designed (2)______ all fitness levels, from beginners to advanced athletes.
Not only do we feature cardio and strength training areas, but we also offer yoga, pilates, and engaging group classes (3)______you motivated. With (4)______ you can easily choose the right plan that fits your schedule and lifestyle. At FitLife Gym, you'll experience the support of our dedicated team in a friendly and encouraging (5)______ . Join us today to kickstart your health journey and discover the difference that a supportive community can (6)______a difference in reaching your fitness aspirations!"
Căn cứ đầu tiên để lựa chọn nghề nghiệp trong lĩnh vực công nghệ là:
Read the passage carefully. Choose an option (A, B, C or D) that best answers each question from 23 to 30.
1. How do children learn about wildlife? And is what they learn the sort of thing they should be learning? It is my belief that children should not just be acquiring knowledge of animals but also developing attitudes and feelings towards them based on exposure to the real lives of animals in their natural habitats. But is this happening?
2. Some research in this area indicates that it is not. Learning about animals in school is often completely disconnected from the real lives of real animals, with the result that children often end up with little or no understanding or lasting knowledge of them. They learn factual information about animals, aimed at enabling them to identify them and have various abstract ideas about them, but that is the extent of their learning. Children's storybooks tend to personify animals as characters rather than teach about them.
3. For direct contact with wild and international animals, the only opportunity most children have is visiting a zoo. The educational benefit of this for children is often given as the main reason for doing it but research has shown that zoo visits seldom add to children's knowledge of animals – the animals are simply like exhibits in a museum that the children look at without engaging with them as living creatures. Children who belong to wildlife or environmental organizations or who watch wildlife TV programmes, however, show significantly higher knowledge than any other group of children studied in research. The studies show that if children learn about animals in their natural habitats, particularly through wildlife-based activities, they know more about them than they do as a result of visiting zoos or learning about them in the classroom.
4. Research has also been done into the attitudes of children towards animals. It shows that in general terms, children form strong attachments to individual animals, usually their pets, but do not have strong feelings for animals in general. This attitude is the norm regardless of the amount or kind of learning about animals they have at school. However, those children who watch television wildlife programs show an interest in and affection for wildlife in its natural environment, and their regard for animals in general is higher.
What could be the best title for the passage?
Read the following passage about lifelong learning and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions from 31 to 40.
[I] Lifelong learning is the ongoing, voluntary, and self-motivated pursuit of knowledge for personal or professional development (Knowles, 2020). [II] This concept emphasizes that learning does not stop after formal education, but rather continues throughout an individual's life, adapting to changing circumstances and needs. [III] In today’s fast-paced world, where technology and job markets evolve rapidly, lifelong learning has become increasingly essential. [IV]
One of the primary benefits of lifelong learning is its ability to enhance employability. Individuals who engage in continuous education are more likely to keep their skills relevant and competitive in the job market. According to a report by the World Economic Forum (2021), over 50% of employees will need reskilling due to technological advancements in the coming years. Lifelong learners are better equipped to adapt to these changes, making them more attractive candidates for employers.
Moreover, lifelong learning contributes to personal fulfillment and mental well-being. Engaging in new learning experiences can stimulate the brain, foster creativity, and improve cognitive function. Research indicates that individuals who pursue learning opportunities throughout their lives tend to report higher levels of happiness and life satisfaction (Smith & Johnson, 2019). Whether it is taking a course, learning a new language, or picking up a new hobby, the process of acquiring knowledge can be enriching and enjoyable.
In addition, lifelong learning promotes social engagement and community involvement. Participating in educational programs or community workshops can foster connections with others who share similar interests. This social aspect of learning can enhance one's sense of belonging and support networks, which are crucial for mental health (Jones, 2022).
Overall, lifelong learning is not just an individual responsibility; it requires support from educational institutions, employers, and communities to create an environment conducive to continuous education. By fostering a culture of learning, society can better prepare individuals for the challenges of the future and ensure that everyone has the opportunity to thrive.
(Adapted from The Importance of Lifelong Learning by Knowles, Smith, Johnson, and others)
Where in paragraph I does the following sentence best fit?
Lifelong learning encourages individuals to embrace new skills and knowledge throughout their lives.
Để khắc phục tình trạng lạm phát do lượng tiền mặt trong lưu thông đã vượt quá mức cần thiết, nhà nước cần làm gì?
Hình chóp S.ABC có , ABC là tam giác vuông tại B, AB = a, BC = 2a. Khi đó khoảng cách từ B đến mặt phẳng (SAC) bằng?
Bảng số liệu dưới đây biểu thị khối lượng, đơn giá và đơn giá trung bình của một số loại thực phẩm mà siêu thị mini nọ bán được trong 3 ngày liên tiếp: ngày thứ nhất, ngày thứ hai và ngày thứ ba.
Biết trong 3 ngày này:
Tổng khối lượng thịt heo bán được gấp đôi tổng khối lượng cá hồi bán được.
Tổng khối lượng thịt bò bán được nhiều hơn tổng khối lượng thịt gà bán được là 20kg.
Tổng khối lượng tôm sú bán được bằng tổng khối lượng mực sữa bán được.
Giá bán mực sữa trong ngày thứ hai là
Cho tam giác \(ABC\) có \(A\left( 0;3 \right);\,B\left( -1;2 \right);\,C\left( 2;1 \right)\). Có bao nhiêu giá trị nguyên của tham số \(m\) để điểm \(M\left( m;\frac{2m-1}{2} \right)\) nằm bên trong tam giác \(ABC\)?
Cho bảng số liệu sau:
GIÁ TRỊ XUẤT NHẬP KHẨU CỦA KHU VỰC MỸ LA TINH NĂM 2014 - 2022
(Đơn vị: tỷ USD)
Năm
2014
2022
Xuất khẩu
681,5
837,1
Nhập khẩu
749,6
915,3
(Nguồn: Trang Thống kê của Tổ chức Thương mại Thế giới)
Căn cứ vào bảng số liệu, cho biết cán cân xuất nhập khẩu của khu vực Mỹ La tinh vào năm 2014 và 2022 lần lượt là bao nhiêu tỷ USD?
Tế bào là đơn vị cấu trúc của cơ thể sống là vì
Trước cách mạng tư sản, xã hội các nước Âu - Mỹ xuất hiện giai cấp mới nào sau đây?
Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.
A new law may soon be passed to deal with the problem.
Trên vỏ một tụ điện có ghi 1000μF−63 V. Điện tích tối đa có thể tích cho tụ có giá trị llà