Câu 1:(2,0 điểm): 1) Tìm các số đối của: - 2; 4; 7; -5. 2) Xácđịnh giá trị tuyệt đối của các số:0; - 4 ; 6; - 25. Câu 2: (4,0 điểm): 1) Tính: a) (- 5) + (- 20); b)(- 16)+ 6; c)1 - (-5); d)(-8).3 2) Thực hiện các phép tính: a) 35 - 12.(3 +4); b) 36 +4.(7- 10); c) (- 3).2²; d)(-6- 14):(-4) Câu 3: (1,5 điểm): Tính: a) [(-10) + (-5)]+(- 25); Câu 4: (1,0 điểm): a) Tìm tất cả các ước của - 6; Câu 5:(1,5 điểm): 1) Tìm số nguyên x, biết: a) x + 10 = 16; b) 5x - 16 = 34 2) Tính tổng tất cả các số nguyên x thoả mãn: - 4

X-48=19+18 ......tìm hiệu của số tròn chục lớn nhất có 2 chữa số có số tròn chục bé nhất có 2 chữ số

Vì sao vào những ngày trời nóng, hanh khô thì ko nên lau màn hình vi tính, ti vi mà chỉ nên dùng chổi lông quét nhẹ thôi.

Giúp em bài số 6,7,8, đi ạ em cảm ơn ❤️❤️

Làm giúp mình câu này với ạ Cho biểu thức A = 17 + (x - y) - (10 - y - x) a) Rút gọn biểu thức A b) Tính giá trị biểu thức A, biết x = 12 ; y = 21

cho tam giác ABC cân tại a (góc a<90°).Kẻ BD vuông góc AC (D€AC), kẻ CE vuông góc AB (E€AB). chứng minh rằng AD=AE b,gọi I là Giao điểm của BD và CE.CHỨNG minh AI là tia phân giác góc A c, tính độ dài BC, biết AD=7cm DC=1cm

A. PHONETICS I. Choose the words that have the different stress from the others. 1.​A. iconic​B. monument​C. territory​D. difficulty 2.​A. Singapore​B. Philippines​C. Canada​D. India 3.​A. native​B. perhaps​C. whisky​D. accent 4.​A. official​B. excursion​C. Thanksgiving​D. spectacle 5.​A. festive​B. Arctic​C. unique​D. speaker B. VOCABULARY AND GRAMMAR II. Complete the sentences, using the correct form of the words in brackets. 1.​We’ll have a long way to walk if we (run) ​​​ out of petrol here. 2.​If you shake that bottle of port, it (not be) ​​​ fit to drink. 3.​If you (wear) ​​​ a false beard, nobody would have recognized you. 4.​I’ll probably get lost unless he (come) ​​​ with me. 5.​You (not have) ​​​ so many accidents if you drove more slowly. C. READING III. Read the following passage and then answer the questions below it. ​Air pollution is a cause of ill-health in human beings. In a lot of countries there are laws limiting the amount of smoke which factories can produce. Although there isn’t enough information on the effects of smoke in the atmosphere, doctors have proved that air pollution causes lung diseases. ​The gases from the exhausts of cars have also increased air pollution in most cities. The lead in petrol produces a poisonous gas which often collects in busy streets surrounded by high buildings. Children who live in areas where there is a lot of lead in the atmosphere cannot think as quickly as other children and they are clumsy when they use their hands. ​There are other long-term effects of pollution. If the gases in the atmosphere continue to increase, the earth’s climate may become warmer. A lot of the ice near the Poles may melt and may cause serious floods. 1.​What can make people sick? ​​ 2.​Where does smoke come from? ​​ 3.​Can air pollution cause lung diseases? ​​ 4.​What else can cause air pollution in cities? ​​ 5.​Why does the earth’s climate become warmer? ​​ IV. Read the passage, and choose the correct answer A, B, C or D for each question. Saving the Environment: One Home at a Time ​Pollution can be seen not only throughout the world, but also in our own homes. It comes from household chemicals, the amount of water people use and the waste people produce and throw away. What can be done to stop this pollution? Surprisingly, a person can help save the environment by doing simple things. ​First, we need to recycle, which allows products to be used over and over again. Recycling can also reduce the number of trees cut down to produce paper products. It takes very little effort. It is not hard to place plastic and glass bottles, aluminum cans and paper in a bin. Anyone can do it. ​Second, we need to watch the amount of water used at home. It can be conserved by taking short showers instead of baths, repairing leaky faucets, using the dishwasher or washing machine only when fully loaded, or simply turning the faucet off while brushing your teeth. ​Third, we need to reduce waste. We need to recycle whenever possible, but should also try to use this waste effectively. For example, grass clippings and food scraps can be made into compost for plants. The average person produces 4.3 pounds of waste every day, but we can reduce that amount by recycling and reusing. ​If we do our part in our own homes, we can help keep the planet from becoming more polluted. 1.​Pollution is caused from the following sources except ​​. ​A. water in rivers​B. water from households ​C. wastes​D. house chemicals 2.​Recycling can help us ​​. ​A. never cut down trees​B. produce more paper products ​C. place garbage bins easily​D. use products again and again 3.​In order to save water, we can do all of the following things except ​​. ​A. fully use the washing machine ​B. repair leaky faucets ​C. take short showers instead of baths ​D. turn the faucet off while brushing your teeth 4.​Recycling helps to reduce waste because ​. ​A. plants need to develop ​B. waste can be recycled and reused ​C. a person can do it in his home ​D. an average man produces compost for plants 5.​The word “It” in paragraph 2 refers to ​​. ​A. cutting down​B. the number ​C. recycling​D. effort

câu 1 thui ak mong các bạn giúp đỡ

Giải giúp em câu 16, 17, 18 với ạ

goi ten cac chet sau theo danh phap IUPAC: CH4;C2H4;C2H6;C3H6;C3H8.