Đáp án: 2b^3+6a^2b
Giải thích các bước giải:
=a^3+3a^2b+3ab^2+b^3 - a^3+3a^2b-3ab^2+b^3
= 2b^3+6a^2b
\(( a + b )^3 -( a - b )^3\)
\(=a^3+3a^2b+3ab^2+b^3-(a^3-3a^2b+3ab^2-b^3)\)
\(=a^3+3a^2b+3ab^2+b^3-a^3+3a^2b-3ab^2+b^3\)
\(=6a^2b+2b^3=2b(3a^2+b^2)\).
Đề bài Mark the letter A, B, C or D to indicate the sentence that is closest in meaning to each of the following question. Question 1. “No, I won’t work overtime at the weekend,” said Sally. A. Sally proised to work overtime at the weekend. B. Sally apologized for not working overtime at the weekend. C. Sally refused to work overtime at the weekend. D. Sally regretted not working overtime at the weekend. Question 2. We survived that accident because the driver was driving carefully. A. But for the driver, we would have survived that accident. B. If we weren’t driving carefully, the driver couldn’t have survived that accident. C. Had the driver not been driving carefully, we wouldn’t have survived that accident. D. Without our seat belts, we could have survived that accident. Question 3. Jenny is so creative that we all can rely on her original ideas. A. Being creative, we can all rely on Jenny for original ideas. B. So creative is Jenny that we all can rely on her for original ideas. C. Jenny is such creative girl that we all rely on her for original ideas. D. Creative though Jenny is, we can rely on her for original ideas. Mark the letter A, B, C or D to indicate the sentence that best combines each pair of sentences in the questions. Question 4. He called to tell me that he was studying. However, I didn’t believe him because there were a party-like sound. A. Though he was studying when he called, I thought he was lying because he phoned, I didn’t believe his claim that he was studying. B. Because of the sounds of a party I heard in the background when he phoned, I didn’t believe his claim that he was studying. C. Although he rang me to tell me that he was studying , I couldn’t hear what he was saying properly because of my unbelievably noisy party. D. I didn’t believe that he could study properly with the noise of a party in the background and and I told him that when he telephoned. Question 5. There were over two hundred people at Carl’s trial. Most of them believed that he was not guilty of the crime. A. The majority of the more than 200 people at Carl’s trial didn’t think that he had committed the crime. B. Carl had not committed the crime, and so more than 200 people came to his trial to show their support. C. Over 200 people coming to Carl’s trial must have influenced the fact that he was found guilty of the crime. D. When it was announced that Carl had been found not guilty of the crime, there were 200 people in the audience at his trial. Mark A, B, C or D to indicate the underlined part that needs correction in each of the questions. Question 6. My brother usually asks (A) me for help when (B) he has (C) difficulty to do (D) his math homework. Question 7. Many people object to use (A) physical punishment (B) in dealing with (C) discipline problems at school. (D) Question 8. Such animals like (A) frogs have (B) waterproof (C) skin that prevents them (D) from drying out quickly in air, sun, or wind. Read the passage and mark A, B, C or D to indicate the correct word that best fits each of the questions. In the early twentieth century, an American woman named Emily Post wrote a book (9)_______ etiquette. This book explained the proper behavior Americans should follow in many different social situations from birthday parties to funerals. But in modern society, it is not simply to know the proper (10)______ for behavior in your own country. It is necessary for people who work or travel abroad to understand the rules of etiquette in other cultures as well. Cultural differences can be found in such simple processes as giving or receiving a gift. In Western cultures, a gift can be given to the receiver with relatively (11)______ ceremony. When a gift is offered, the receiver usually takes the gift and expresses his or her thanks. In Chinese culture, both the giver and receiver understand that the receiver will typically refuse to take the gift several times before he or she finally accepts it. In addition, to show respect for the receiver, it is (13)_________ in several Asian cultures to use both hands when offering a gift to another person.
What lessons have you got today?
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chứng minh rằng số đường chéo của 1 đa giác lồi n cạnh là $\frac{n(n-3)}{2}$
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Trong bài báo cáo kết quả thực hành đo độ dài, 1 HS đã ghi 1 = 20,5 cm. Hãy cho biết HS đã dùng thước có ĐCNN là bao nhiêu?? M.n giúp mk nha, T2 mk nộp r ạk ><
Xét tính chẵn le của hàm số -y= -2sinx
trường trong mơ (bằng tiếng anh)
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