đặt một điểm sáng S tại tiêu điểm chính của một thấu kính hội tụ có trục chính Δ rồi liên tiếp dịch chuyển S trên Δ theo ra xa thấu kính .gọi S' là ảnh của S tạo bời thấu kính.khi S cách thấu kính 25cm thì khoảng SS' ngắn nhất.tiêu cự của thấu kính có giá trị gần nhất là A.123 cm B.10 cm C.không tính được D.0 cm giải thích nữa

Pt: x² - 2mx + 2m - 3 = 0 a) Chứng minh phương trình luôn có 2 nghiệm phân biệt với mọi m b) Tìm m để x²1 + x²2 + x1 × x2 = 15

Calli chữ " Chúc mừng sinh nhật Hoài❤️❤️" Thật là đẹp nha 1 píc kí 1 píc ko Ko app Ko ô li, kẻ ngang Sử dụng bút chuyên dụng Calli thật đẹp có tâm Có trang trí Hóng~~~~~

Hoà tan 27,8 gam tinh thể MSO4.nH2O vào nước thì thu được V ml dung dịch A. Cho Ba(NO3)2 dư vào V ml dung dịch A thu được 23,3 gam kết tủa. Mặt khác cho NaOH dư vào V ml dung dịch A thì thu được 9,0 gam kết tủa. Xác định công thức của tinh thể

giúp em với e cần gấp ( 5 sao vs 1 cảm ơn ạ )

Vẽ anime cầm bánh sinh nhật có dòng chữ " Chúc Hoài sinh nhật vui vẻ 6/6/2008" Yc : Đẹp , có tâm Ko ô li , kẻ ngang,... Có trang trí thật đẹp Nhường dân chuyên vẽ 1 píc kí 1 píc ko Ko vẽ qua loa cho xong Phải thật đẹp nha Digi/Tradi đều đc Hóng~~~~

Tính nhanh D:1/8+1/16+1/32+1/64+1/128

Read the following passage and mark the letter A, B, C or D to indicate the correct word or phrase that best fits each of the numbered blanks. Some people believe that soon schools will no longer be necessary. They say that (23) _______ the Internet and other new technologies, (24) _______ no longer any need for school buildings, formal class, or teachers. Perhaps this will be true one day, but this is hard to (25) _______ a world without schools. In fact, we need to look at how we can use new technology to make schools better, not (26) _______ them. We should invent a new kind of school that is (27) _______ to libraries, museums, science centers, laboratories, and even companies. 23. A. despite B. because of C. thought D. because 24. A. there are B. they are C. it is D. there is 25. A. know B. realize C. imagine D. consider 26. A. to eliminate B. eliminative C. eliminator D. elimination 27. A. limited B. linked C. contributed D. addressed Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions. Unlike life in the countryside which is often considered to be simple and traditional, life in the city is modern and complicated. People, from different regions, move to the cities in the secretaries of having a better life for them and their children. The inhabitants in city work as secretaries, businessmen, teachers, government workers, factory workers and even street vendors or construction workers. The high cost of living requires city dwellers, especially someone with low income, to work harder or to take a part-time job. For many people, an ordinary day starts as usual by setting up in the early morning to do exercise in public parks. Preparing for a full day of working and studying, then travelling along crowed boulevards or narrow streets filled with motor scooters and returning home after a busy day. They usually live in large houses, or high-rise apartment blocks or even in a small rental room equipped with modern facilities, like the Internet, telephone, television and so on. Industrialization and modernization as well as global integration have big impact on lifestyle in the cities. The most noticeable impact is the Western style of clothes. The “ao dai” - Vietnamese traditional clothes are no longer regularly worn in Vietnamese women’s daily life. Instead, jeans, T-shirts and fashionable clothes are widely preferred. 28 Industrialization and modernization may lead to industrialization and modernization may lead to _________. A. some changes in lifestyles B. global integration C. the fact that women no longer wear Ao Dai D. the disappearance of Western-styled clothes 29. The most important reason why people move to the city is that _________. A. to have busy days B. to look for a complicated life C. to look for a better life D. to take part-time jobs 30. We can infer from the passage that _________. A. there is a big gap between the rich and the poor in the city. B. people leave the countryside because life there is simple C. most of the urban dwellers have low income D. people do morning exercise in public parks because they have much free time 31. According to the passage, the city life can offer city dwellers all of the following things EXCEPT _________. A. a variety of jobs in different fields B. modern facilities C. the Internet D. friendly communication with neighbours 32. The word “impact” in paragraph 2 is closest in meaning to _________. A. situation B. effect C. force D. action

bài 1: Tính nhanh a) 12.48 :0.5 x 6.25 x 4 x 2 b) 2 x 3.12 x 1.25 : 0.25 x 10

Mọi người giải giúp em theo hình bên dưới. EM CẢM ƠN.