Hãy dung phương pháp hóa học phân biệt các lọ khí mất nhãn sau: a) Oxi,hidro,Nito b) Oxi,hidro,cacbon

$\lim_{n \to \infty} \frac{n^6+4n}{3n^6-3n^4+2n^2-1}$

III. Choose the best answer a, b, c or d to complete the sentence. 1. You should walk across the street ______ the zebra crossing. a. on b. at c. in d. from 2. My house is not far from my school, so I usually go ______. a. on foot b. by foot c. by car d. by boat 3. This morning, I was ______ in a traffic jam and got to school fifteen minutes late. a. catch b. block c. struck d. stuck 4. Turn on the left turn ______ before you make the turn and slow down. a. sign b. direction c. signal d. crossing 5. It is ______ to use a hand-held mobile phone while driving or riding. a. safe b. important c. illegal d. careful 6. ______ does it take you to ride to school? – About 30 minutes. a. How long b. How far c. How often d. How much 7. A ______ is a part of a road that only bicycles are allowed to use. a. cycle cross b. cycle lane c. cycle line d. cycle race 8. You ______ cross the street when the light is red. a. should b. don’t have to c. can d. mustn’t 9. People ______ produce as much rubbish as we do now. a. use to b. used to c. used to not d. didn’t use to 10. “How far is Vung Tau from Ho Chi Minh City”-“_______” A. It’s not very far b. it takes about two hours or more. c. It’s about 120km d. You can get to Vung Tau by boat or bus. IV. Write the correct from or tense of verbs in brackets. 1. ____________________ (you/ ever/ drive) on the wrong side of the road? 2. My family ______________ (fly) back from our Hong Kong holiday two days ago. 3. Right now, the students _______________ (learn) road signs in the schoolyard. 4. Usually Oanh ______________ (walk) to school, but this week she _____________ (ride) her bike. 5. The driver was so drunk that he ______________ (lose) control of his car. 6. If I have enough money, I _________________ (buy) a racing car. 7. My father ________________ (teach) me to ride a bike when I was seven. 8. Transport used ______________ (be) much slower three hundred years ago. 9. Saudi women weren’t allowed ______________ (drive) a car until recently. 10. In South Africa, you have to let animals ________________ (go) first. V. Supply the correct form of the words in brackets 1. Young children are expected to show _____________ to their parents. (obey) 2. When cycling on the roads, remember: _____________ first. (safe) 3. Children should avoid _____________ foods such as hamburger and chips. (health) 4. Most road accidents happen because the motorists drive _____________. (care) 5. It is unsafe and _____________ to pass another vehicle on the left. (legal) 6. My _____________ was delayed for over two hours due to bad weather. (fly) 7. Everyone should _____________ obey traffic rules for their own safety. (strict) 8. The policeman _____________ the car to stop with a flashlight. (sign) 9. Signs with red circles are mostly _____________ - that means you can’t do something. (prohibit) 10. This _____________ sign indicates that traffic lights are ahead. (warn)

phương trình(m-1)x^2+2(m-1)x+3=0 có nghiệm kép khi m bằng bao nhiêu Giúp mình với ạ

Cho tam giác ABC vuông tại A, BM là đường trung tuyến. a) Biết AB = 6cm, AM= 4cm. Tính BC. b) Trên tia đối của tia MB lấy điểm N sao cho BM=MN. Chứng minh tam giác MBA = tam giác MNC. c) Chứng minh: AB+ BC > 2BM giải hộ mình với ạ,,,,,,,

Một lớp học có 52 học sinh bao gồm ba loại: Gioi ,Khá ,Trung bình .Số học sinh trung bình chiếm 7/13 số học sinh cả lớp .Số học sinh khá bằng 5/6 số học sinh còn lại .Tính số học sinh giỏi của lớp

Giúp mình giải câu này với mọi người ạ!!!😢

Giúp mình câu 8,9,10,11,12,13,14 vs ạ

`text( Cho đa thức f(x))` `text(xác định với mọi x thỏa mãn)` `x.f(x+2) = (x^2 -9)f(x)`

Ở 1 tế bào sinh dục trong giảm phân, kì giữa I thoi phân bào không hình thành, kì sau I, cuối I diễn ra bình thường, kết quả sau giảm phân 2 là: A. Tạo nên 2 tế bào lưỡng bội (2n) B. Tạo 1 tế bào tứ bội (4n) C. Tạo 4 tế bào con đơn bội (n) D. Tạo 4 tế bào lưỡng bội (2n)