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Lily Nguyễn
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Thảo Phương
28 tháng 12 2021 lúc 10:34

Chọn D. Cồn là 1 hỗn hợp vì trong cồn 70 độ gồm C2H5OH và nước

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Quỳnhh-34- 6.5 Phạm như
16 tháng 3 2022 lúc 20:14

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Nguyễn thảo
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Hương Vy
7 tháng 12 2021 lúc 20:18

1 his illness, he cannot come

2 her busyness, she couldn't help us

3 his illness, he tries to go to school on time

4 the bad weather, we tried to finish the work on the road

5 the bad weather, we got to the station late

6 the old house, she liked it

7 not wearing any shoes, Carol ran outside to see what was happening

8 being afraid of flying, Fiona had to get on the plane

Vy trần
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Vũ Đức Anh
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Thuỳ Linh Nguyễn
9 tháng 8 2023 lúc 9:03

thiếu đề ạ 

Quý Trương
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Đỗ Thanh Hải
7 tháng 6 2021 lúc 14:00

9 Although the girl works hard from morning till night, her step mother isn't happy

10 Rice is grown in tropical countries

11 The countryside is more peaceful than the city, but I prefer living in the city

12 A lot of Chung Cakes are made on Tet holiday

13 Although Little Pea works hard from morning till night, her mother isn't happy

14 An ordinary car goes more slowly than a sport car

15 An's sister performs better than him

16 Many fesstivals are held by the Thai every year

17 I enjoy hanging out with my best friends

18 If you don't hurry up, you will be late for the race

Đặng Thị Mỹ Linh
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Nguyễn Hoàng Minh
25 tháng 10 2021 lúc 15:01

\(a,A=\dfrac{x+2\sqrt{x}+1+x-2\sqrt{x}+1-3\sqrt{x}-1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\\ A=\dfrac{2x-3\sqrt{x}+1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}=\dfrac{\left(\sqrt{x}-1\right)\left(2\sqrt{x}-1\right)}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}=\dfrac{2\sqrt{x}-1}{\sqrt{x}+1}\\ b,A=\dfrac{2\left(\sqrt{x}+1\right)-3}{\sqrt{x}+1}=2-\dfrac{3}{\sqrt{x}+1}\in Z\\ \Leftrightarrow\sqrt{x}+1\inƯ\left(3\right)=\left\{1;3\right\}\left(\sqrt{x}+1\ge1\right)\\ \Leftrightarrow\sqrt{x}\in\left\{0;2\right\}\\ \Leftrightarrow x\in\left\{0;4\right\}\left(tm\right)\)

ILoveMath
25 tháng 10 2021 lúc 15:03

a) \(A=\dfrac{\sqrt{x}+1}{\sqrt{x}-1}+\dfrac{\sqrt{x}-1}{\sqrt{x}+1}-\dfrac{3\sqrt{x}+1}{x-1}\)

\(\Rightarrow A=\dfrac{\left(\sqrt{x}+1\right)^2}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}+\dfrac{\left(\sqrt{x}-1\right)^2}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}-\dfrac{3\sqrt{x}+1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\)

\(\Rightarrow A=\dfrac{x+2\sqrt{x}+1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}+\dfrac{x-2\sqrt{x}+1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}-\dfrac{3\sqrt{x}+1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\)

\(\Rightarrow A=\dfrac{x+2\sqrt{x}+1+x-2\sqrt{x}+1-3\sqrt{x}-1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\)

\(\Rightarrow A=\dfrac{2x-3\sqrt{x}+1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\)

\(\Rightarrow A=\dfrac{\left(2x-2\sqrt{x}\right)-\left(\sqrt{x}-1\right)}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\)

\(\Rightarrow A=\dfrac{2\sqrt{x}\left(\sqrt{x}-1\right)-\left(\sqrt{x}-1\right)}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\)

\(\Rightarrow A=\dfrac{\left(2\sqrt{x}-1\right)\left(\sqrt{x}-1\right)}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\)

\(\Rightarrow A=\dfrac{2\sqrt{x}-1}{\sqrt{x}+1}\)

Quân Đào
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Ngọc Phạm thanh
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Ngô Ngọc Tâm Anh
6 tháng 1 2022 lúc 20:09

kt giữa kì ??? nếu vậy thì em không giúp