Đáp án:
`m ne -2`
Giải thích các bước giải:
`mx+y=5`
`<=>y=5-mx` thế vào pt dưới
`=>2x-(5-mx)=-2`
`=>2x+mx-5=-2`
`=>x(m+2)=3`
Để pt có nghiệm duy nhất
`=>m+2 ne 0=>m ne -2`
Từ $mx+y=5\to y=5-mx$Thay $y=5-mx$ vào $2x-y=-2$, ta có:$2x-(5-mx)=-2$
$↔2x-5+mx=-2$$↔x(2+m)=3$Để hệ phương trình có nghiệm duy nhất thì $2+m\ne0$$↔m\ne-2$Vậy $m\ne-2$ thì hệ phương trình có nghiệm duy nhất.
Giúp mik bài này vs, mik cần gấp
1. Manh (read) the newspaper if he went by train. Bài 2: Viết lại câu sao cho nghĩa không đổi 1. He wrote the letter in two hours. It took 2. I was very interested in our conversation. It was interesting 3. I haven’t been to the dentist’s for two years. It’s 4. I spent seven years at secondary school and then I went to university. After 5. It’s my opinion that you should take more exersise. If I 6. It’s thought that the accident was caused by human error. The accident is 7. The questions are so easy that everyone can answer them. They’re such 8. The boy will receive some money to continue his study. His parents died in a traffic accident The boy whose 9. They are producing motorbikes in Vietnam. Motorbikes are 10. If you do not try hard, you can’t pass the examination. Unless 11. He went to London. He had lived there when he was a boy. He went to London where 12. Although she said that she would come, I don’t think she ever will. Despite 13. My father used to play football when he was young. My father doesn’t 14. Jane gave me a present on my last birthday. I was 15. We got lost in the jungle because we didn’t have a map. If we had 16. I last saw Bob when I was in Ho Chi Minh City. I haven’t seen 17. It is a three-hour drive from Hanoi to Nam Dinh. It takes 18. When did you first know him? How 19. It may rain hard this afternoon, so take the rain coat with you. In case 20. If you don’t rest yourself you really will be ill Unless 21. How tall is Peter’s father? What giúp với cần gấp
Cần gấp giúp mình với. Thanks!!!
tìm sô nguyên tố p sao cho p+14 và p+28 là sôs nguyên tố
giải phương trìnhhhhhhhhhhhhhhhhhhhhhhh
Giúp mình với mình cần gấp lắm ạ !!!!!!!!!!!
Bài 4: Cho đường tròn , đường thẳng d không đi qua O và cắt đường tròn tại hai điểm phân biệt A và B. Từ một điểm C trên d (C nằm ngoài đường tròn ) kẻ hai tiếp tuyến CM, CN với đường tròn (M, N là các tiếp điểm). Gọi H là trung điểm của AB, đường thẳng OH cắt tia CN tại K. a)Chứng minh: 4 điểm C, O, H, N cùng nằm trên một đường tròn. b)Chứng minh: KN . KC = KH . KO. c)Một đường thẳng đi qua O và song song với MN cắt các tia CM, CN lần lượt tại E, F. Xác định vị trí của điểm C trên d sao cho tam giác CEF có diện tích nhỏ nhất. mong mn help mình
cho biểu thức A= căn x+3/căn x-2 và B= 1/ căn x-2 + 1/căn x+2 - x/4-x a, cho x=16. tính A b, rút gọn B c, tìm x để B(căn x-2) + 2căn x = x -căn 7(x-2) +7
1. If I ...... you, I .... volunteer to clean the beach. A. am/will B. was/ will C. am/would D. were/would 2. If our school .... the tree planting project, I .... join in. A. organises/will B. organises/ would C. organised/ would D. organised/will 3. Without water, there .... no lives on the earth so we have to reduce water pollution. A. was B. were C. will be D. would be 4. A: ............. B: That's the reason why I usually have headaches. A. This song sounds great. B. The river is seriously contamianated. C. Our city has too much noise pollution. D. You ate too much raw meet tonight. 5. A: ............. B: Let's clean it up. A. The rooom is so dirty. B. Air pollution does harm to our health. C. Farmers use too much pesticide that badly affetcs soil and small animals. D. What do you think about water pollution in our neighbourhood? 6. The polluted water results .... the death of several creatures A. in B. on C. of D. for 7. The reduction in air pollution was ...... last year. A. drama B. dramatic C. dramatise D. dramatically 8. In many poor nations, there are frequent outbreaks of cholera and other diseases because people there ........ untreated water. A. drink B. to drink C. drinking D. drank 9. .......water is one of the factors that have driven many species to the verge of extinction A. Contaminating B. Contaminated C. Contaminant D. Contamination 10. Too much carbon dioxide in the atmosphere causes global ....... A.warm B. warming C. warmly D. warmth 11. Environmental pollution has ........ to lots of health problems. A. caused B. led C. made D. resulted 12. _____ industrial waste, many fish cannot survive. A. Because B. Since C. As D. Because of 13. Choose the word which has a different stress pattern from the others. A. medical B. hospital C. politic D. eletric 14. Choose the word which has a different stress pattern from the others. A. physical B. horrific C. beautiful D. different 15. The sight of too many advertising billboards, overhead poles and shop signs causes __________ pollution A. air B. light C. visual D. noise 16. When thermal pollution happens, the water temperature in streams, rivers, lakes and oceans __________. A. changes B. keeps C. remains D. stays 17. Choose the word which has a different stress pattern from the others. A. national B. chemical C. medical D. informal 18. Oil spills from cargos and ships have _____ many animals and plants die. A. made B. resulted C. caused D. led 19. If we ........... glass, we ......... air pollution by 20 percent. A. recycle/reduce B. recycled/ reduced C. recycle/ will reduce D. recycled/ would reduce Read the passage and decide whether the following statements are True or False? Air pollution is a serious problem in many cities. Motor vehicles, factories and other sources create so much air pollution that it may hang in the air like dirty fog. Air pollution threatens the health of the people who live in cities. City wastes cause water pollution when they are poured into the water-ways. These wastes kill fish and make some areas unfit for swimming. In addition, many large cities have difficulties in disposing of their garbage. The amount of garbage grows each year, but places to put it are quickly filling up. Citizens, governments, industries, scientists, and business people must work together in different ways to gradually reduce pollution. For example, most cities have introduced recycling programmes. Tùy chọn 1 1. Motor vehicles and factories are among some sources of air pollution. True False 2. Air pollution doesn’t endanger people’s health in some cities. True False 3. Air pollution is the only problem of the environment mentioned in this passage True False 4. Garbage disposal is a problem in many large cities. True False 5. Everyone must cooperate to reduce pollution. True False 6. We can reduce pollution by recycling programmes only. True False các bn làm chính xác giúp mik nha đây là bài kiểm tra của mik đấy các pro giúp mik nha chính xác đấy
Nêu điểm khác biệt về thành phần và phương thức diệt trừ sâu hại giữa chết phẩm Bt và NPV?
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