Anh chj giúp em câu 1 với ạ
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Em đg ôn đề trực tuyến anh chj giúp em 3 câu này với ạ 
I don't know how to play the game.
This department is to the left of the post office.
Phương án 1, nhưng phải sửa là with a ball under the table.
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I don't know how to play the game.
This department is to the left of the post office.
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Em cần là câu 4 đó ạ , mong anh chj giúp :
Talk about your dream job Các anh chj giúp em vs ạ Các anh chj làm ngắn ngắn giúp em
Câu hỏi thắc mắc bài khó nên các anh chj giup em với gấp lắm ạ
tính
1+1/3+1/6+1/10+...+1/45
dấu gạch là phần ạ
các anh chj tính giúp em với ạ
Đặt A = \(1+\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{45}\)
\(\frac{1}{2}A=\frac{1}{2}+\frac{1}{6}+\frac{1}{20}+...+\frac{1}{90}\)
\(=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\)
\(=1-\frac{1}{10}\)
\(A=\frac{9}{10}.2\)
\(=\frac{9}{5}\)
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Đặt \(A=1+\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{45}\)
=> \(\frac{1}{2}A=\left(1+\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+....+\frac{1}{45}\right).\frac{1}{2}\)
\(=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}\)
\(=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+....+\frac{1}{9.10}\)
= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+.....+\frac{1}{9}-\frac{1}{10}\)
= \(1-\frac{1}{10}=\frac{9}{10}\)
=> A= 9/10:1/2=9/5
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Ta có \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{45}\Rightarrow\frac{1}{2}\left(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{45}\right)=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}\)
\(=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{9}-\frac{1}{10}\)
\(=\frac{1}{2}-\frac{1}{10}=\frac{4}{10}=\frac{2}{5}\Rightarrow\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{45}=\frac{2}{5}:\frac{1}{2}=\frac{4}{5}\)
Vậy \(1+\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{45}=1+\frac{4}{5}=\frac{9}{5}\)
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làm giúp em bài 6 trên hình vs anh chj ạ
Cho em hỏi các anh chj nhe ( em lớp 5)
Oxit là cái gì ạ, có cùng họ hàng với axit ko ạ, nó có ăn mòn ko?
em cảm ơn anh chj nếu trả lời đc
Oxit là hợp chất gồm 2 nguyên tố hóa học trong đó có một nguyên tố là oxy
Chắc là Oxit không ăn mòn á , bạn có thể nghiên cứu trên mạng về õit
![Yuri Sweet[𝕿𝖊𝖆𝖒 𝕹𝖊𝖕𝖆𝖑]](https://hoc24.vn/images/avt/avt6428199_256by256.jpg)
Oxit axit là oxit của Phi kim .
Phi kim : ví dụ : S(Lưu huỳnh) ,N(Nitơ) ,C(Cacbon) ,P(Photpho) ...
Các loại oxit axit : ví dụ : \(SO_2,SO_3,NO,CO,CO_2,P_2O_5\)
Xem thêm câu trả lời
Các anh chj giúp em với ạ~~I. Choose the best answer A, B, C or D to complete the following sentences.1. The new apartment has a lot of modern things. It is well-__________A. empty B. beautiful C. furnished D. nervous2. Which is the national anthem of Vietnam? A. Tieu Doan 307 B. Chien si Viet Nam C. TienQuanCa D. Tienve Ha Noi3. Can you see any people in the house ? - __________ A. only a little...
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Các anh chj giúp em với ạ~~
I. Choose the best answer A, B, C or D to complete the following sentences.
1. The new apartment has a lot of modern things. It is well-__________
A. empty B. beautiful C. furnished D. nervous
2. Which is the national anthem of Vietnam?
A. Tieu Doan 307 B. Chien si Viet Nam C. TienQuanCa D. Tienve Ha Noi
3. Can you see any people in the house ? - __________
A. only a little B. only few C. only a few D. only little
4. __________ she plays the piano!
A. How well B. How good C. What well D. What good
5. After break, everyone goes __________ and classes start again.
A. indoor B. indoors C. outdoor D. outdoors
6. He learns _______ the guitars everyday.
A. play B. to play C. playing D. plays
7. __________ my students are familiar with this kind of school activities.
A. Most B. Most of C. A few D. Few
8. She looks like you. She __________ your sister.
A. must be B. perhaps C. must D. may
9. What is the name of the girl __________ to Mrs. Lien?
A. talk B. talks C. talking D. is talking
10. Would you __________ show me a nice picture, Ann?
A. like B. mind C. to D. please
11. Janna can’t play the piano, and Carol can’t play it __________.
A. either B. too C. neither D. as well
12. Saxophones are used mainly for __________ jazz music.
A. composing B. taking C. playing D. writing
13. I went to the 3D __________ last weekend. The paintings were excellent!
A. movie theater B. concert hall C. opera house D. art museum
14. __________ I’m not a fan of country music, I thoroughly enjoyed his lively performance.
A. Although B. Because C. As D. However
15. __________ does a water puppet show take place? ~ In a pool.
A. What B. When C.How D. Where
I. Choose the best answer A, B, C or D to complete the following sentences.
1. The new apartment has a lot of modern things. It is well-__________
A. empty B. beautiful C. furnished D. nervous
2. Which is the national anthem of Vietnam?
A. Tieu Doan 307 B. Chien si Viet Nam C. TienQuanCa D. Tienve Ha Noi
3. Can you see any people in the house ? - __________
A. only a little B. only few C. only a few D. only little
4. __________ she plays the piano!
A. How well B. How good C. What well D. What good
5. After break, everyone goes __________ and classes start again.
A. indoor B. indoors C. outdoor D. outdoors
6. He learns _______ the guitars everyday.
A. play B. to play C. playing D. plays
7. __________ my students are familiar with this kind of school activities.
A. Most B. Most of C. A few D. Few
8. She looks like you. She __________ your sister.
A. must be B. perhaps C. must D. may
9. What is the name of the girl __________ to Mrs. Lien?
A. talk B. talks C. talking D. is talking
10. Would you __________ show me a nice picture, Ann?
A. like B. mind C. to D. please
11. Janna can’t play the piano, and Carol can’t play it __________.
A. either B. too C. neither D. as well
12. Saxophones are used mainly for __________ jazz music.
A. composing B. taking C. playing D. writing
13. I went to the 3D __________ last weekend. The paintings were excellent!
A. movie theater B. concert hall C. opera house D. art museum
14. __________ I’m not a fan of country music, I thoroughly enjoyed his lively performance.
A. Although B. Because C. As D. However
15. __________ does a water puppet show take place? ~ In a pool.
A. What B. When C.How D. Where
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