`A=2+2^2+...+2^100``A=2.1+2.2+...+2.2^99``A=2(1+2+...+2^99)\vdots2(1)``A=2+2^2+...+2^100``A=(2+2^2)+...+(2^99+2^100)``A=2(1+2)+...+2^99(1+2)``A=2.3+...+2^99. 3``A=3(2+...+2^99)\vdots3(2)`Mà ` Ư CLN(2;3)=1(3)`Từ `(1);(2);(3)=>A \vdots6`Vậy `A\vdots3;2;6`
Đáp án + Giải thích các bước giải:
`A=2+2^{2}+....+2^{100}`
`=(2+2^{2})+(2^{3}+2^{4})+....+(2^{99}+2^{100})`
`=(2+2^{2})+2^{2}(2+2^{2})+....+2^{98}(2+2^{2})`
`=6+2^{2}.6+....+2^{98}.6`
`=6(1+2^{2}+....+2^{98})\vdots 2;3;6`
Vậy `A\vdots 2;3;6`
Hurry, it's urgent 1. Which of the following is NOT mentioned as a reason why better lighting had become necessary by the mid- nineteenth century? A. development of railroads B. demand for better medical facilities C. increases in the number of new factories D. growth of cities 2. The phrase "served as" inline 5 is closest meaning to ___________. A. differed from B. functioned as C. rested upon D. reacted to 3. The word "this" in line 7 refers to ___________. A. lard B. charcoal C. wick D. oil 4. Which of the following is NOT mentioned as a disadvantage of camphene? A. high cost B. bad smell C. potential to explode D. greasy texture 5. What can be inferred about the illuminating gas described in the paragraph? A. It was first developed in the United States. B. It was not allowed to be used in public buildings, C. It was not widely available until mid- century. D. It had an unpleasant smell. 6. The word "resembled" in line 17 is closest in meaning to____. A. was similar to B. cost the same as C. was made from D. sounded like 7. According to the passage, what advantage did the kerosene patented by Gesner have over camphene? A. Kerosene had a more pleasant smell. B. Kerosene was less expensive. C. Kerosene burned more brightly. D. Kerosene was safer to use. 8. The word "it" in line 18 refers to_____. A. fortune B. odor C. camphene D. kerosene 9. Which of the following best describes the organization of the passage? A. A description of events in chronological order B. A comparison of two events C. An analysis of scientific findings D. The statement of a theory and possible explanations 10. Where in the passage does the author mention the origin of a word? A. Lines 4-6 B. Lines 7-8 C. Lines 12-13 D. Lines 14-17
1. I last phoned my aunt last week. ->I haven't.. 2. Maria last visited us five months ago.->Maria has. 3. Linda hasn't written diary for two months. →Lan didn't......... 4. Lan and Maryam have corresponded for three years. ->It is three years. 5. It's two years since I saw her. -> I have 6. I haven't been to the dentist's for two years. -> It's.. 7. They haven't seen my friend for one month. -> It is one month. 8. Nam hasn't worn this shirt before. ->It's the first time.. 9. John has not had his hair cut for over six months. -> It is. 10. They haven't phoned us for a month. -> It is.... 11. Mary has never been to that place before. ->It's. 12. They have never read such an interesting story before. ->This is 13. This is the first time I have tasted that cake. ->I have.. 14. The last time I saw him was ten years ago. ->It's... 15. I haven't played volleyball since I was a student. ->The last time.. 16. She has never been so unhappy before. ->This is the first time.. 17. I have never met that man before. ->this is the first time... 18. My mom has never been so happy before. ->this is the first time... 19. Nam hasn't read that novel before. ->It's... 20. I have never worn Ao dai before. ->this is the first time... 21. Linda has never heard that before. ->This is the first time... 22. Mary hasn't seen that notice here before. -> It's.. 23. We have cooked the meal since he came. ->We started. 24. It's two years since I saw her. -> I haven't.... 25. I last saw Bob when I was in Ho Chi Minh City. -> I haven'tseen.. 26. We have never read such boring news before. → This is.... 27. They have never done such an easy exercise before. → This is 28. I haven't met that boy before. ->This is the first time.... 29. Linh bought this computer 5 month ago. →Linh have used
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hết điểm rồi mong đc câu trả lời đúng
Qủa dưa hấu phát tán chủ yếu nhờ hình thức nào ? Càng nhanh càng tốt
Để trung hòa a gam dung dịch NaOH 10 % cần dùng vừa đủ 100 ml dung dịch H2SO4 IM. (a) Viết PTPƯ xảy ra. (b) Tính a. alaba trap :>>>>>>>>>>>>>>>>>>>>>>>>>>>
phân tích đa thức thành nhân tử x ³ - 2x - 4
Chứng mình S chia hết cho 4 S=3+3^2+3^3+...+3^99+3^100
Giải thích và chọn đáp án giúp em với nhé
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