Gọi d là ƯCLN(n+1, 3n+2) (d∈N*)
⇒n+1$\vdots $d và 3n+2$\vdots$d
⇒3(n+1)$\vdots$d và 3n+2$\vdots$d
⇒3n+3$\vdots$d và 3n+2$\vdots$d
⇒3n+3-(3n+2)$\vdots$d
⇒1$\vdots$d
⇒d=1
⇒ƯCLN(n+1, 3n+2)=1
Vậy phân số đó tối giản với mọi n
Một tàu thủy dự định đi từ bến A đến bến B nếu tàu thủy đi với vận tốc 42km/h thì đến bến B chậm hơn dự định 1 giờ. Nếu tàu thuỷ đi với vận tốc 56km/h thì đến bến B trước dự định 30 phút. Hỏi quãng đường tàu thủy đi từ bến A đến bến B dài bao nhiêu km?
hãy tính 45% của 680 và nêu cách tính 10% của 680 là......... 30% của 680 là...... 5% của 680 là
Tìm tất cả ca cặp số tự nhiên (x, y) thỏa mãn: 2020^x = 2y ² - 6y + 5
#mấy anh chị giỏi Anh giúp em vs I. Choose the word whose the underlined part is pronounced differently from that of the others. 1. A. blankets B. prepositions C. weekends D. partners 2. A. gather B. entrance C. family D. banyan 3. A. played B. invited C. modernized D. stayed 4. A. about B. found C. council D. course 5. A. floor B. bamboo C. booth D. food II. Use the correct form of the verbs in brackets. 1. Look! A girl (ride) _____________ a water buffalo. 2. Loan (not finish) _________________ her homework yet. 3. They used (write) ______________ to each other every month when they were at school. 4. We wish we (know) _____________________ his decision now. 5. They (practice) _________________________ their music lesson last night? III. Choose the best answer. 1. Mr Smith is going to buy a new car, ……….? A. doesn’t he B. is he C. isn’t he D. does he 2. Peter has lived far from his parents and friends______2 years. A. since B. in C. for D. during 3. He wishes he _________speak English fluently. A. could B. will C. can D. does 4. She asked me if I_______ a driving license. A. have B. having C. had D. to have 5. People didn’t do everything with the help of modern equipment, _______? A. they did B. didn’t they C. did it D. did they 6. Would you like to go to the cinema with me _______ Sunday evening? A. in B. at C. to D. on 7. I _________English here since I graduated from university. A. teach B. taught C. have taught D. am teaching 8. Liz will visit Ba’s village again if she _________to Viet Nam next year. A. return B. returned C. would return D. returns 9. It rains heavily, _________I can’t go to the movies with you. A. and B. but C. because D. so 10. If Nam worked hard, he ___________ a lot of money. A. will earn B. would earn C. earns D. earned IV. Find and correct the mistakes in the following sentences. 1. I wish (A) I can (B) travel to (C) the countryside next week (D). 2 Minh said he invited (A) his (B) friends to have (C) dinner the next (D) weekend. 3. The letter (A) should been (B) delivered (C) in the afternoon (D). 4. Minh has (A) a big house (B) in the city (C) , hasn’t (D) he? 5. Would (A) you mind (B) give (C) me a (D) lift? V. Choose the correct options in the box to fill in the blanks in order to make a complete passage and answer the questions below. broken; invented; shortage; is; papermaking; exported; Paper was __________ (1) by the Chinese in the first century A.D. The art of papermaking took 700 years to reach the Muslim world and another 700 years to get to Britain. Most paper __________ (2) made from wood. When the trees are cut down, they are carried by land or water to paper mills. Here they are cut up and the wood is __________ (3) up into fibers, mixed with water and chemicals. This wood pulp is then dried up on a machine and made into paper. Papermaking is an important British industry, and paper from Britain is __________ (4) to South Africa, Australia and many other countries. Some of the wood used in British __________ (5) industry comes from trees grown in Britain, but wood is also imported from other countries such as Norway. One tree is needed for every 400 copies of a forty-page newspaper. If half the adults in Britain each day buy one daily paper, this uses up over 40,000 trees a day. Trees are cut down faster than they can be replaced, so there may be a paper __________ (6) before the year 2030. VI. Complete the second sentence so that it has the same meaning as the first one. 1. Lan cannot visit her pen pal in Malaysia. ->Lan wishes she…………………………………………………………………………… 2. “Don’t stay up so late”, my father said. -> My father told me……………………………………………………………………….. 3. We repainted the house last week. -> The house ……………………………………………………………………………….. 4. Karen learnt to play the piano when he was young, so he can play it very well now. -> Because …………………………………………………………………………….. 5. Try to study hard and you will pass the exam -> If……………………………………………………………………………….. 6. They last met each other when they graduated -> They haven’t ….……………………………………………………………….. 7. It rains so heavily, so we stop the match. -> If……………………………………………………………………………….. VII. Write complete sentences using the suggested words . 1. Would / mind / if /I/ borrow / your car? -> ………………………………………………………………………………………….. 2. He asked / if / I / be / free / that night. -> ……………………………………………………………………………
tính chu vi và diện tích hình tròn có đường kính là 4,5 dm
Giúp mình làm 2 bài 3 và 5 với mình cần gấp
viết đoạn văn khoảng 12 đến 14 câu theo phương pháp lập luận tổng -phân-hợp trình bày cảm nhận của em về vẻ đẹp của nhân vật 'tôi' trong một lần phá bom .Đoạn văn có sử dụng lời dẫn trực tiếp và phép thế dùng để liên kết (gạch chân dưới lời dẫn trực tiếp và phép thế)
Câu 9: Kết quả dãy tính sau tận cùng bằng chữ số nào? 2001.2002.2003.2004 + 2005.2006.2007.2008.2009 Câu 10: Tìm số tự nhiên x biết: a) 720 : (x - 17) = 12 b) (x - 28) : 12 = 8 c) 26 + 8x = 6x + 46 d) 3600 : [(5x + 335) : x] = 50
Lan và Mai mua tất cả 30 cái khẩu trang. Lan cho bạn Hồng 4 cái khẩu trang và cho bạn Mai 3 cái khẩu trang thì Lan có ít hơn Mai 2 cái khẩu trang. Hỏi lúc đầu Lan mua mấy cái khẩu trang? Mấy chị giải dùm em bài này đúng em cho ctlhn và lời cám ơn, 5 sao nha nhưng phải là ai nhanh hơn
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