Bài 1: a) Nếu tổng của 2 số tự nhiên là 1 số lẻ, thì tích của chúng có thể là 1 số lẻ được không? b) Nếu tích của 2 số tự nhiên là 1 số lẻ, thì tổng của chúng có thể là 1 số lẻ được không? c) “Tổng” và “hiệu” hai số tự nhiên có thể là số chẵn, và số kia là lẻ được không?

a, Tìm đa thức bậc hai biết f(x)- f(x-1) =x . Từ đó áp dụng tính tổng `S = 1 + 2 + 3 + ............. + n` b, Cho `(2bz - 3cy)/a = (3cx - az)/2b = (ay - 2bx)/3c` . Chứng minh `x/a = y/(2b) = z/(3c)`

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vào 10h45' ngày 30/4/1975 có sự kiện j vào 11h30' ngày 30/4/1975 có sự kiện j

ahihi cái này là đọc đoạn văn xong coi true hay false thui UwU 32 (5)

25. While he was washing his car, Mr. Brown _______a small dint in the rear fender. A. has discovered B. was discovering C. is discovering D. discovered 26. The earth _______ on the sun for its heat and light A. is depended B. depends C. is depending D. has depended 27. I’m busy at the moment _______on the computer A. I work B. I’m worked C. I’m working D. I worked 28. At this time tomorrow _______over the Atlantic A. we’re flying B. we’ll be flying C. we’ll fly D. we’re to fly 29. Our friends _______next us at the airport tonight A. are B. are going to C. go to D. will be to 30. When I entered the room, everyone _____________. A. has been dancing B. was dancing C. had danced D. danced 31. He said that he _________ his homework since 7 o’clock. A. had done B. did C. has done D. was doing 32. How long __________ able to drive? - Since 1990. A. could you B. have you been C. were you D. are you 33. She won't get married until she __________ 25 years old. A. is B. will be C. had been D. was. 34. This building used to be a library,_________? A. doesn't it B. didn’t it C. isn’t it D. wasn’t it 35. Nobody was injured in the accident, ________? A. was there B. was he C. were they D. wasn't it 36. Let's go out for a walk, ______? A. not us B. don't we C. do we D. shall we 37. Jane and I________ school in 1987. A. finish B. have finished C. finishes D. finished 38. John and Ann ………. married last Saturday. A. get B. got C. is getting D. have got 39. His brother…………….high school 6 years ago A. finish B. finished C. finishes D. has finished 40. We have been living here………...1990 A. for B. from C. since D. during 41. Pasteur _____ in the 19th century. A. was living B. lived C. had lived D. has lived 42. .Now my sister _____ a bicycle of her own. A. is having B. are having C. has D. had 43 .Don’t bother me while I ……………….. A. am working B. was working C. will work D. will have completed 44 .How ................since we ................school? A. are you / left B. will you be / had left C. have you been / left D. had you been/ had left 45. When he came.......................... A. I was watching TV B. I watched TV C. I am watching TV D. I have watched TV 46. The piano _____ at the moment. A. repairs B. repaired C. is repaired D. is being repaired 47. I saw Jack yesterday morning while I ________ home from work. A. walked B. was walking C. am walking D. had been walking 48. My brother................out at weekend. A. doesn’t usually go B. does usually not go C. doesn’t usually goes D. usually doesn’t goes. 49. Everyday, my sister .................the floor. A. usually clean B. cleans usually C. usually cleaned D. usually cleans 50. Your English …………wonderfully since last month. A. improved B. was improved C. have improved D. has been improved

Câu 1:Giữa cường độ dòng điện và độ sáng của bóng đèn có mối liên hệ như thế nào? Câu 2: 15A = ………….mA 1200mA = ………….A 2,5V = ………….mV 3500mV = ………….V

a, `|x-2|+ |3-2x | = 2x +1` b,Tìm x;y biết `xy + 2x -y =5` c, Tìm x;y;z biết `2x = 3y; 4y = 5z` và `4x - 3y + 5z =7`

Cau hoi: Xét đúng (sai) mệnh đề và phủ định mệnh đề sau : \(\forall x \in \mathbb{R}\) \({x^4} - {x^2} + 1 = \left( {{x^2} + \sqrt 3 x + 1} \right)\left( {{x^2} - \sqrt 3 x + 1} \right)\) A. Mệnh đề \(\forall x \in \mathbb{R},\,\,{x^4} - {x^2} + 1 = \left( {{x^2} + \sqrt 3 x + 1} \right)\left( {{x^2} - \sqrt 3 x + 1} \right)\) đúng Mệnh đề phủ định là \(\exists x \in \mathbb{R},\,\,{x^4} - {x^2} + 1 \ne \left( {{x^2} + \sqrt 3 x + 1} \right)\left( {{x^2} - \sqrt 3 x + 1} \right)\). B. Mệnh đề \(\forall x \in \mathbb{R},\,\,{x^4} - {x^2} + 1 = \left( {{x^2} + \sqrt 3 x + 1} \right)\left( {{x^2} - \sqrt 3 x + 1} \right)\) đúng Mệnh đề phủ định là \(x \in \mathbb{R},\,\,{x^4} - {x^2} + 1 \ne \left( {{x^2} + \sqrt 3 x + 1} \right)\left( {{x^2} - \sqrt 3 x + 1} \right)\). C. Mệnh đề \(\forall x \in \mathbb{R},\,\,{x^4} - {x^2} + 1 = \left( {{x^2} + \sqrt 3 x + 1} \right)\left( {{x^2} - \sqrt 3 x + 1} \right)\) sai Mệnh đề phủ định là \(\exists x \in \mathbb{R},\,\,{x^4} - {x^2} + 1 \ne \left( {{x^2} + \sqrt 3 x + 1} \right)\left( {{x^2} - \sqrt 3 x + 1} \right)\). D. Mệnh đề \(\forall x \in \mathbb{R},\,\,{x^4} - {x^2} + 1 = \left( {{x^2} + \sqrt 3 x + 1} \right)\left( {{x^2} - \sqrt 3 x + 1} \right)\) sai Mệnh đề phủ định là \(x \in \mathbb{R},\,\,{x^4} - {x^2} + 1 \ne \left( {{x^2} + \sqrt 3 x + 1} \right)\left( {{x^2} - \sqrt 3 x + 1} \right)\)

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