Đáp án + giải thích các bước giải :
`sqrt{x-1) = x-4` $\text{(Điều kiện : x $\geq4$)}$ $\\$ ` \Leftrightarrow (sqrt{x-1))^2 = (x-4)^2 ` $\\$ ` \Leftrightarrow x - 1 = x^2 - 8x + 16` $\\$ ` \Leftrightarrow x^2 - 9x + 17 = 0` $\\$ ` \Leftrightarrow x^2 - 2 . 9/2 . x + (9/2)^2 + 17 - (9/2)^2 = 0` $\\$ ` \Leftrightarrow (x-9/2)^2 - 13/4 = 0` $\\$ ` \Leftrightarrow (x-9/2 - sqrt13/2)(x-9/2 + sqrt13/2 )= 0` $\\$ ` \Leftrightarrow [(x-9/2 - sqrt13/2 = 0),(x-9/2 + sqrt13/2 =0):} \Leftrightarrow [(x=(sqrt13 + 9)/2),(x= (-sqrt13+9)/2):} ` $\\$ `Vậy : x = (sqrt13 + 9)/2 ; x = (-sqrt13+9)/2`
$\sqrt{x-1}$ = $x-4$
⇔ $(\sqrt{x-1})^{2}$ = $(x-4)^{2}$
⇔ $x-1$ = $x^{2} - 8x + 16$
⇔ $x^{2} - 9x +17 = 0$
⇔ $Δ = b^{2} - 4ac = (-9)^{2} - 4.1.17 = 13$
⇔ $\sqrt{Δ} = \sqrt{13}$
⇔ $x_{1} = \frac{-b-\sqrt{Δ}}{2a} = \frac{9-\sqrt{13}}{2}$
$x_{2} = \frac{-b+\sqrt{Δ}}{2a} = \frac{-9-\sqrt{13}}{2}$
Cho a;b là 2 số nguyên dương và nguyên tố cùng nhau CMR tồn tại các số nguyên x;y sao cho ax+by=1 Mn giúp e vs e cho 5* ah
Vẽ anime hoặc manga về 1 nhân vật ngầu, có màu
X chia hết cho 24 và 42 x là số nhỏ nhất khác 0
Cần siêu gấp ạk giúp với đăng lần 2 ruiff
mọi người giúp mình với ạ hứa vote 5sao
Bài 3:Tính tổng a) 1+2+3+4+5+…..+100 b) 1+3+5+7+9+…..+99 c) 1+5+9+13+…….+101
Tìm tất cả các giá trị của m để phương trình cosx = 2m - 5
làm nhanh ạ làm trước 20h10 hôm nay ạ ai nhanh nhất sẽ đc ctlhn
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions. New York has Central Park; London has Hyde Park while Kuala Lumpur has its own piece of green belt amidst the hustle and bustle of city life. It's an ideal place for a leisurely stroll in a tranquil setting, all without having to leave the city. The Lake Gardens was created by Sir Alfred Venning, who persuaded the ruling government to allow him to turn a swamp land into rambling trails with man-made lakes, spanning 60 hectares. However, as the city expanded, the Lake Gardens reduced in size. But it is still a sizeable area and boasts of more than just grass and water within its grounds. For example, the gardens incorporate the National Monument, Bird Park, Hibiscus Garden as well as Malaysia's Parliament House. Additionally, Carcosa Seri Negara is on a hilltop overlooking the Lake Gardens. Today, the nineteenth-century British colonial mansion has been converted into an exclusive hotel. 29. According to the passage, what do New York, London and Kuala Lumpur have in common? A. They each have a lake in the city. B. They each have a swamp land in the city. C. They each have a park in the middle of the city. D. They each have a 60-hectare garden in the city. 30. In the Lake Gardens, you can visit the following spaces EXCEPT _______. A. Hyde Park B. the Bird Park C. the Hibiscus Garden D. the National Monument 31. Over time, the Lake Gardens has become smaller because_______. A. it is swampy B. the city developed C. it is too noisy D. it is getting overpopulated 32. The word “converted” in the last sentence is closest in meaning to_______. A. built B. consumed C. made D. changed 33. We’ll get there early so that we’ll be able to get tickets. A. If we get there early, we’ll be able to get tickets. B. If we don’t get there early, we’ll be able to get tickets. C. If we get there early, we won’t be able to get tickets. D. Unless we get there early, we’ll be able to get tickets. 34. “Close your books and go out to play”, the teacher said to us. A. The teacher told us close our books and go out to play. B. The teacher told us to closing our books and go out to play. C. The teacher told us closing our books and go out to play. D. The teacher told us to close our books and go out to play. 35. My dad worked in a factory in the past, but doesn’t work there now. A. My dad used to working in a factory. B. My dad used to be working in a factory. C. My dad used to work in a factory. D. My dad used to be work in a factory. 36. Mr. Peter has written a lot of articles for the CNN News. A. A lot of articles have written for the CNN News by Mr. Peter. B. A lot of articles have been written for the CNN News by Mr. Peter. Mark letter A, B, C or D on your answer sheet to indicate the sentence that is closest in meaning to the original sentence in each of the following questions. C. A lot of articles has written for the CNN News by Mr. Peter. D. A lot of articles has been written for the CNN News by Mr. Peter. 37. Although he was tired, he finished doing his homework. A. In spite his tiredness, he finished doing his homework. B. In spite of his tiredness, he finished doing his homework. C. In spite of he was tired, he finished doing his homework. D. In spite his tired, he finished doing his homework. 38. He is a much slower speaker than my brother. A. He speaks much more slowly than my brother. B. He doesn’t speak much more slowly than my brother. C. He speaks much more quickly than my brother. D. He doesn’t speak much more quickly as my brother. 39. They often went to school by bike when they were young. A. They used go to school by bike when they were young. B. They used to going to school by bike when they were young. C. They used to go to school by bike when they were young. D. They used to went to school by bike when they were young. 40. She has taught her children to play piano for 4 years. A. She started teaching her children to play piano 4 years ago. B. She started to teaching her children to play piano 4 years ago. C. She started teaching her children to play piano for 4 years ago. D. She started teaching her children to play piano since 4 years.
Mn giúp em 2 câu e,f thoi ạ em cảm ơn
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