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Nguyễn Thị Quỳnh Như
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Khánh Linh
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Lê Phạm Phương Trang
3 tháng 3 2022 lúc 18:52

1. many -> much

2. a apple -> an apple

3. Theirs -> Their

4. ???

5. visiting -> to visit

6. were -> was

Thái Hoà Nguyễn
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Dung Thi My Tran
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Nguyễn Hoàng Minh
13 tháng 11 2021 lúc 11:01

\(26,\\ a,\sin45^0=\cos45^0< \sin50^025'< \sin57^048'=\cos32^012'< \sin72^0=\cos18^0< \sin75^0\\ b,\tan37^026'< \tan47^0< \tan58^0=\cot32^0< \tan63^0< \tan66^019'=\cot23^041'\\ 27,\\ A=\dfrac{\left(\sin^226^0+\sin^264^0\right)+2\left(\cos^215^0+\cos^275^0\right)}{\left(\sin^255^0+\cos^255^0\right)+\left(\sin^242^0+\cos^242^0\right)}-\dfrac{\tan81^0}{2\tan81^0}\\ A=\dfrac{\left(\sin^226^0+\cos^226^0\right)+2\left(\sin^215^0+\cos^215^0\right)}{1+1}-\dfrac{1}{2}\\ A=\dfrac{1+2}{2}-\dfrac{1}{2}=2-\dfrac{1}{2}=\dfrac{3}{2}\)

\(28,\\ \sin^2\alpha=1-\cos^2\alpha=1-\dfrac{1}{2}=\dfrac{1}{2}\\ \Leftrightarrow\sin\alpha=\dfrac{\sqrt{2}}{2}\)

Đặng Thảo
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Nguyễn Trần Thành Đạt
10 tháng 8 2021 lúc 7:28

Em ơi đăng tách bài ra mỗi lượt đăng 1-2 bài thôi nha!

Lê Hồng MInh
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Nguyễn Lê Phước Thịnh
8 tháng 5 2021 lúc 22:29

ĐKXĐ: \(x\notin\left\{0;-9\right\}\)

Ta có: \(\dfrac{1}{x+9}-\dfrac{1}{x}=\dfrac{1}{5}+\dfrac{1}{4}\)

\(\Leftrightarrow\dfrac{20x}{20x\left(x+9\right)}-\dfrac{20\left(x+9\right)}{20x\left(x+9\right)}=\dfrac{4x\left(x+9\right)+5x\left(x+9\right)}{20x\left(x+9\right)}\)

Suy ra: \(4x^2+36x+5x^2+45x=20x-20x-180\)

\(\Leftrightarrow9x^2+81x+180=0\)

\(\Leftrightarrow x^2+9x+20=0\)

\(\Leftrightarrow x^2+4x+5x+20=0\)

\(\Leftrightarrow x\left(x+4\right)+5\left(x+4\right)=0\)

\(\Leftrightarrow\left(x+4\right)\left(x+5\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x+4=0\\x+5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-4\left(nhận\right)\\x=-5\left(nhận\right)\end{matrix}\right.\)

Vậy: S={-4;-5}

Lê Hồng MInh
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Kiêm Hùng
8 tháng 5 2021 lúc 21:50

Hướng làm:

Thấy cả tử mẫu cộng lại đều bằng 2021 → Cộng thêm 1 rồi quy đồng với mỗi phân thức

\(\dfrac{x+2}{2019}+1+\dfrac{x+3}{2018}+1=\dfrac{x+4}{2017}+1+\dfrac{x}{2021}+1\\ \Leftrightarrow\dfrac{x+2021}{2019}+\dfrac{x+2021}{2018}-\dfrac{x+2021}{2017}-\dfrac{x+2021}{2021}=0\\ \Leftrightarrow\left(x+2021\right)\left(\dfrac{1}{2019}+\dfrac{1}{2018}-\dfrac{1}{2017}-\dfrac{1}{2021}\right)=0\\ \Leftrightarrow x+2021=0\Leftrightarrow x=-2021\)

Trần Mạnh
8 tháng 5 2021 lúc 21:51

\(< =>\dfrac{x+2}{2019}+1+\dfrac{x+3}{2018}+1=\dfrac{x+4}{2017}+1+\dfrac{x}{2021}+1\)

\(< =>\dfrac{x+2+2019}{2019}+\dfrac{x+3+2018}{2018}=\dfrac{x+4+2017}{2017}+\dfrac{x+2021}{2021}\)

\(< =>\dfrac{x+2021}{2019}+\dfrac{x+2021}{2018}-\dfrac{x+2021}{2017}-\dfrac{x+2021}{2021}=0\)

\(< =>\left(x+2021\right)\left(\dfrac{1}{2019}+\dfrac{1}{2018}-\dfrac{1}{2017}-\dfrac{1}{2021}=\right)=0\)

\(< =>x+2021=0< =>x=-2021\)

Vậy....

 

Đặng Thảo
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hnamyuh
8 tháng 8 2021 lúc 6:24

Bài 2 : (1) liên kết ; (2) electron ; (3) liên kết ; (4) : electron ; (5) sắp xếp electron

Bài 4 : 

$\dfrac{M_X}{4} = \dfrac{M_K}{3} \Rightarrow M_X = 52$

Vậy X là crom,KHHH : Cr

Bài 5 : 

$M_X = 3,5M_O = 3,5.16 = 56$ đvC

Tên : Sắt

KHHH : Fe

hnamyuh
8 tháng 8 2021 lúc 6:30

Bài 9 : 

$M_Z = \dfrac{5,312.10^{-23}}{1,66.10^{-24}} = 32(đvC)$

Vậy Z là lưu huỳnh, KHHH : S

Bài 10  :

a) $PTK = 22M_{H_2} = 22.2 = 44(đvC)$

b) $M_{hợp\ chất} = X + 16.2 = 44 \Rightarrow X = 12$
Vậy X là cacbon, KHHH : C

Bài 11 : 

a) $PTK = 32.5 = 160(đvC)$

b) $M_{hợp\ chất} = 2A + 16.3 = 160 \Rightarrow A = 56$
Vậy A là sắt

c) $\%Fe = \dfrac{56.2}{160}.100\% = 70\%$

hnamyuh
8 tháng 8 2021 lúc 6:33

Bài 12 : 

a) $M_{hợp\ chất} = R + 1.4 = M_O = 16(đvC) \Rightarrow R = 12$

Vậy R là nguyên tố cacbon, KHHH : C

b) $\%C = \dfrac{12}{16}.100\% = 75\%$

Bài 13 : 

a) $PTK = 32M_{H_2} = 32.2 = 64(đvC)$

b) $M_{hợp\ chất} = X + 16.2 = 64 \Rightarrow X = 32$
Vậy X là lưu huỳnh, KHHH : S

Han Nguyen
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Komorebi
7 tháng 3 2021 lúc 23:25

8. As it is raining heavily, we can't go on a picnic

9. I suggest (that) you should get a plumber to check the pipes

10. If you don't succeed, you'll have to try it again

11. If she had enough money, she would buy the dictionary

12. I suggest using gas instead of burning coal

13. I suggest you should install a burglar alarm in your house

14. If we recycle, we will save natural resources

15. If you don't hurry up, you will be late for work

16. If you work too much, you will be tired

17. I suggest putting different kinds of.....

18. Lan broke the glass as she was careless

19. If you litter the place around you, it will be a junk yard

20. Paul suggested using public transportation

21. If she doesn't reduce the use of water and electricity, she will have to.....

22. Since the weather was snowy, we postponed our soccer match

23. Tan suggested that Lam should buy a car

24. Lan suggested that I should look for another job

25. The scientist suggested using public transportation instead of private vehicles

26. giống c12

27. The principle is pleased that the students in grade 9 are good helpers

28. If we put garbage into the bins, we will minimize pollution

29. If you are careless, you will broke the vase

30. If you don't stop cutting trees, I will call the police

31. If you use electricity to catch fish, you will be fined heavily

32. I'm sure that that boy will have a test.....

33. We are disappointed that you threw the rubbish on the street

34. It is extremely important that all of us work together to protect the environment

35. I'm sorry that I couldn't do anything to help you

36. He is sure that environmental pollution in this area can be controlled

37. She was annoyed that he damaged the car yesterday