Cho A={x∈R∣−4x2−2x+6=0}. Tập hợp A viết bằng cách liệt kê phần tử là
Hãy suy nghĩ và trả lời câu hỏi trước khi xem đáp án
Giải phương trình này:
$4x^2 + 2x - 6 = 0$
$2x^2 + x - 3 = 0$
$2x^2 + 3x - 2x - 3 = 0$
$x(2x + 3) - (2x + 3) = 0$
$(x - 1)(2x + 3) = 0$
$x = 1$ hoặc $x = -\dfrac{3}{2}$.
Vậy $A = \left\{1; \dfrac{-3}{2}\right\}$
Câu hỏi liên quan
Read the following passage about the impact of tweeting on everybody 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 18 to 22
EVERYBODY’S TWEETING
Twitter (18) ________________ for a podcasting website, but then people realized that it offered them the power to connect with millions of people instantly. Suddenly, everyone had a voice, as long as it wasn’t longer than 140 characters. But what are we using it for, and just how is Twitter changing the way we do things?
Perhaps the greatest impact Twitter has had is on breaking news. Before Twitter, (19) _____________ before finally broadcasting it on the radio or TV. These days, anyone who happens to be in the right place at the right time with a Twitter account can post news the second it happens. For example, Janis Krums posted a photo and a tweet when he witnessed a US flight making an emergency landing in the Hudson River. He must never have imagined that he would break the story to the world.
Following Pop Idols
Young people have always loved to follow their pop idols, and Twitter has made it a whole lot easier. Before the Internet, teenagers used to join the fan clubs of their favorite bands and write letters to their heroes,
(20) _________________ to get a reply written by the club secretary. Today’s teenagers don’t need to wait. By following their idols on Twitter, they get all the news the minute it happens: their meals, activities, or even thoughts. And all the news comes directly from the bands themselves.
Creating Movements
Twitter allows people who think the same way to get together and (21) ______________. These problems may be cyberbullying, sexism, or racism. They can share information, organize campaigns, and put pressure on related departments. Twitter has given the man and woman on the street the power to make a difference.
Identifying the source of a piece of news
It’s good to get an idea of the background of a person who says or writes something. Are they an impartial expert or someone who wants to change your opinion to suit their own agenda? For example, this statement about a flu epidemic, “Patients can already spread the virus a day before they’ve even fallen sick themselves”, is more likely to come from a doctor than a politician. On the other hand, “We have to stop people who are carrying the virus from getting into the country” is more likely to come from a politician. (22) _____________, you’re better able to decide how much importance to give it and whether you can really trust what they say.
Trên vỏ một tụ điện có ghi 20 pF – 200 V. Tụ điện tích trữ được năng lượng tối đa là
Mark the letter A, B, C or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions.
“Congratulations on winning the race last week!”, Laura said to Leo.
Cho các nguyên tử sau: F (Z = 9); P (Z = 15); C (Z = 6); Cl (Z = 17); Al (Z = 13). Những nguyên tử nào có cùng số electron lớp ngoài cùng?
Người ta treo một đầu lò xo vào một điểm cố định, và móc vào đầu dưới của lò xo những quả nặng, mỗi quả đều có trọng lượng 2 N. Khi chùm quả nặng có 2 quả thì chiều dài lò xo là 10 cm. Khi chùm quả nặng có 5 quả thì chiều dài lò xo là 15 cm. Chiều dài tự nhiên và hệ số đàn hồi của lò xo là:
Chủ tịch nước sẽ có những nhiệm vụ và quyền hạn nào sau đây?
Lực nào sau đây không thực hiện công khi nó tác dụng vào vật đang chuyển động?
Một vật có khối lượng 0,1kg và động lượng 1kgm/s. Khi đó động năng của vật bằng
Nhóm cây trồng nào sau đây phân loại theo khả năng hóa gỗ?
Phần mềm trình chiếu (Microsoft Power Point) là?
Truyền kì mạn lục của Nguyễn Dữ phản ánh điều gì?
“Where do you think Rooney is today?". "I have no idea. He _______________late."
Hệ thống chữ La-tinh là thành tựu sáng tạo của cư dân quốc gia cổ đại nào?
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 from 13 to 17.
Hello Ethan,
d. Your suggestion for the nature magazine was perfect; it has really broadened my understanding.
b. I hope you’re having a great day!
a. They were incredibly interesting! While I’m currently focused on improving my nature photography skills, I did find the documentaries enlightening.
c. Let’s catch up soon; I’d love to share my recent photos with you!
e. I wanted to say how much I appreciated the wildlife documentaries you sent me last week. Best regards,
Chloe
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.
I was an MBA student in the USA and I lived in the university’s coed dormitory. In my culture, usually, if a woman talks to a man, it is a sign of romantic interest. (34)_____, in the first few days of school, I found it strange that so many women were talking to me and I was under the impression that some women on my dormitory floor were interested in me. To (35)__________ their politeness, I would buy them flowers or offer small gifts, as is done in my country. However, I was quite surprised to see that these same women now seemed (36)______around me. One was even quite offended and told me to leave her alone. Eventually I talked to the residence adviser on my floor to see what I was doing wrong, and he explained to me the way men and women usually interact in the USA. I was quite relieved to hear that (37)____ was wrong with me, but rather with the way I was interpreting my conversations with women. Even though I did not find the love of my life while I was in the USA, I still made many good female friends afterwards (38)______I still maintain contact.
Nguyên nhân nào dưới đây làm vùng Tây Nguyên và Nam Bộ có mùa khô sâu sắc?
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questions.
Taking Home the World Cup
Standing just 36 centimeters tall, the FIFA World Cup Trophy symbolizes the pinnacle of football achievement. Every four years, teams worldwide compete for it, but no one ever takes the trophy home. Made of 18-carat gold, the original trophy remains under FIFA's protection, with winners receiving only a replica. This measure safeguards it from theft, as the trophy has been stolen twice in its history.
The original trophy was made by a French sculptor, Abel LaFleur, and was called the “Jules Rimet Cup,” in honor of the founder of the World Cup tournament. Sometime during the first three World Cup events (1930, 1934, and 1938), the name changed to simply the “World Cup.” Then during World War II, not much was seen or heard of the trophy. It was being kept hidden in a shoe box under the bed of Dr. Ottorino Barassi, the Italian vice-president of FIFA, to prevent it from falling into the hands of the Nazi army. In 1966, the Cup was stolen during a public showing of the trophy prior to the World Cup tournament in England. Luckily, it was found a short time later, none the worse for wear, in a trash container by a little dog named Pickles. Four years later, Brazil earned permanent possession of the original trophy by winning its third World Cup title. Unfortunately, the trophy was stolen a second time in 1983 and was never recovered. The Brazilian Football Association had to have a duplicate trophy made.
(I) After the first trophy became the possession of Brazil’s football association, a new World Cup Trophy for FIFA was designed by an Italian artist, Silvio Gazzaniga, in 1974. (II) This trophy cannot be won outright, but remains in the possession of FIFA, and rest assured they are watching it very closely. Today, World Cup winners are awarded a replica of the trophy that is gold-plated, rather than solid gold like the real one. (III) Gazzaniga’s World Cup trophy weighs almost five kilograms. (IV) Its base contains two layers of a semi-precious stone called malachite, and has room for seventeen small plaques bearing the names of the winning teams---enough space to honor all the World Cup champions up to the year 2038. After that, a new trophy will have to be made.
The word "it" in paragraph 1 refers to:
Biểu hiện nào là kết quả của vận động nội lực theo phương thẳng đứng?
Có tất cả mấy bước lập kế hoạch tài chính cá nhân?
When Jane feared she'd ______ her keys again, she quickly checked to see if they were _________ in her pocket.