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Chữ số 6 có giá trị là 60

=>6 là chữ số hàng chục

5 không nằm ở hàng đơn vị

mà 5 không là chữ số hàng chục

nên 5 là chữ số hàng trăm

=>Chữ số hàng đơn vị là 7

Vậy: Số cần tìm là 567

9 tháng 7

a) Để x là số hữu tỉ dương thì:

\(\dfrac{13-n}{-5}>0\)
Mà: `-5<0` 

`=>13-n<0`

`=>n>13` 

b) Để x là số hữu tỉ âm thì:

`(13-n)/-5<0`

Mà:  `-5<0`

`=>13-n>0`

`=> n<13` 

c) Đê  x không phải số hữu tỉ âm cũng không phải số hữu tỉ dương thì:

\(x=0=>\dfrac{13-n}{-5}=0\\ =>13-n=0\\ =>n=13\)

Bài 2:

Để \(\dfrac{m+2}{5};\dfrac{m-5}{-6}\) đều là các số dương thì

\(\left\{{}\begin{matrix}\dfrac{m+2}{5}>0\\\dfrac{m-5}{-6}>0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}m+2>0\\m-5< 0\end{matrix}\right.\)

=>-2<m<5

mà m nguyên

nên \(m\in\left\{-1;0;1;2;3;4\right\}\)
 Bài 3:

Để \(\dfrac{1-m}{-13};\dfrac{5-m}{3}\) đều là các số âm thì

\(\left\{{}\begin{matrix}\dfrac{1-m}{-13}< 0\\\dfrac{5-m}{3}< 0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{m-1}{13}< 0\\\dfrac{m-5}{3}>0\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}m-1< 0\\m-5>0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}m< 1\\m>5\end{matrix}\right.\)

=>\(m\in\varnothing\)

a: \(-\dfrac{25}{20}< 0;0< \dfrac{20}{25}\)

Do đó: \(-\dfrac{20}{25}< \dfrac{20}{25}\)

b: \(\dfrac{15}{21}=\dfrac{15:3}{21:3}=\dfrac{5}{7};\dfrac{21}{49}=\dfrac{21:7}{49:7}=\dfrac{3}{7}\)

mà 5>3

nên \(\dfrac{15}{21}>\dfrac{21}{49}\)

c: \(\dfrac{-19}{49}=\dfrac{-19\cdot47}{49\cdot47}=\dfrac{-893}{49\cdot47}\)

\(\dfrac{-23}{47}=\dfrac{-23\cdot49}{47\cdot49}=\dfrac{-1127}{47\cdot49}\)

mà -893>-1127

nên \(-\dfrac{19}{49}>-\dfrac{23}{47}\)

9 tháng 7

\(A=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{\left(n-1\right)n}\\ =1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{n-1}-\dfrac{1}{n}\\ =1-\dfrac{1}{n}\\ =\dfrac{n-1}{n}\)

\(B=\dfrac{49}{2\cdot9}+\dfrac{49}{9\cdot16}+\dfrac{49}{16\cdot23}+...+\dfrac{49}{65\cdot72}\\ =7\cdot\left(\dfrac{7}{2\cdot9}+\dfrac{7}{9\cdot16}+\dfrac{7}{16\cdot23}+...+\dfrac{7}{65\cdot72}\right)\\ =7\cdot\left(\dfrac{1}{2}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{23}+...+\dfrac{1}{65}-\dfrac{1}{72}\right)\\ =7\cdot\left(\dfrac{1}{2}-\dfrac{1}{72}\right)\\ =7\cdot\dfrac{35}{72}\\ =\dfrac{245}{72}\)

\(E=\dfrac{4}{3\cdot7}+\dfrac{4}{7\cdot11}+...+\dfrac{4}{95\cdot99}\)

\(=\dfrac{1}{3}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+...+\dfrac{1}{95}-\dfrac{1}{99}\)

\(=\dfrac{1}{3}-\dfrac{1}{99}=\dfrac{33}{99}-\dfrac{1}{99}=\dfrac{32}{99}\)

\(D=\dfrac{1}{7}+\dfrac{1}{91}+\dfrac{1}{247}+\dfrac{1}{475}+\dfrac{1}{775}+\dfrac{1}{1147}\)

\(=\dfrac{1}{1\cdot7}+\dfrac{1}{7\cdot13}+\dfrac{1}{13\cdot19}+\dfrac{1}{19\cdot25}+\dfrac{1}{25\cdot31}+\dfrac{1}{31\cdot37}\)

\(=\dfrac{1}{6}\left(\dfrac{6}{1\cdot7}+\dfrac{6}{7\cdot13}+...+\dfrac{6}{31\cdot37}\right)\)

\(=\dfrac{1}{6}\left(1-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{13}+...+\dfrac{1}{31}-\dfrac{1}{37}\right)\)

\(=\dfrac{1}{6}\left(1-\dfrac{1}{37}\right)=\dfrac{1}{6}\cdot\dfrac{36}{37}=\dfrac{6}{37}\)

\(C=\dfrac{3}{1\cdot3}+\dfrac{3}{3\cdot5}+...+\dfrac{3}{49\cdot51}\)

\(=\dfrac{3}{2}\left(\dfrac{2}{1\cdot3}+\dfrac{2}{3\cdot5}+...+\dfrac{2}{49\cdot51}\right)\)

\(=\dfrac{3}{2}\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+...+\dfrac{1}{49}-\dfrac{1}{51}\right)\)

\(=\dfrac{3}{2}\left(1-\dfrac{1}{51}\right)=\dfrac{3}{2}\cdot\dfrac{50}{51}=\dfrac{1}{17}\cdot25=\dfrac{25}{17}\)

 

ĐỀ LUYỆN LÊN 6 SỐ 10 Circle the word which has underlined part pronounced differently from the others. (3 points) 1. A. prefer B. better C. teacher D. worker 2. A. bear B. hear C. dear D. near 3. A. collect B. concern C. concert D. combine Circle the odd one out. ( 2 points) 4. A. watches B. brushes C. teacher D. goes 5. A. meat B. fish C. beef D. tea Circle the best option A, B, C or D to complete the sentences. (12 points) 6. Would you like to play tennis, Nam? A. I’d like to, but I...
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ĐỀ LUYỆN LÊN 6 SỐ 10 Circle the word which has underlined part pronounced differently from the others. (3 points) 1. A. prefer B. better C. teacher D. worker 2. A. bear B. hear C. dear D. near 3. A. collect B. concern C. concert D. combine Circle the odd one out. ( 2 points) 4. A. watches B. brushes C. teacher D. goes 5. A. meat B. fish C. beef D. tea Circle the best option A, B, C or D to complete the sentences. (12 points) 6. Would you like to play tennis, Nam? A. I’d like to, but I can’t B. Yes, I’d like to C. No, thanks D. I’d like to go 7. I have some homework. I________ finish it before I play table tennis. A. should to B. need to C. ought D. want 8. Can I borrow your fishing rob, Minh? A. No, I can’t B. I’m sorry, Nam. I‘m using. C. I’d love to D. Yes, please 9. Traffic police never let you________ without a ticket. A. go B. going C. to go D. gone 10. London is ________ of England. A. capital B. the capital C. a capital D. one capital 11. ________ do you go shopping? – Every week. A. How far B. What time C. How often D. How 12. ________ people go to the movies now than ten years ago. A. Fewer B. Few C. Less D. Lesser 13. ________ was in. The room was empty. A. Anybody B. Somebody C. Everybody D. Nobody 14. Would you tell me where________ born. A. you were B. were you C. you was D. was you 15. Tom hates watching T.V. ________ does Peter. A. So B. Too C. Neither D. Either 16. Hoa prefers colorful dances in Thailand________ shadow puppet shows in Indonesia. A. to B. than C. as D. for 17. ________ seeing beautiful sites, visitors can enjoy traditional food. A. Apart B. Together C. According to D. As well as Find one mistake A, B, C or D and correct it (3pts) 18. Would you like going to the movies with me tonight? A B C D 19. My brother doesn’t like pork, and I don’t like them, too. A B C D 20. It takes me two hours doing my homework every day. A B C D Read the passage and answer the questions (5 pts) GETTING BACK TO NATURE The Little Morocco is a beautiful building. We used stone and mud to build the hotel. There are skylights - windows in the roof to let light in - so we save electricity. The skylights give us light in the day, so we don’t use electric lights. We don’t use chemicals to clean the rooms because we don’t want to damage the environment. You can walk in the mountains near the hotel and see lots of local wildlife. Enjoy a boat trip on the lake and see the amazing waterfalls, or visit the beautiful caves. 21. What did they use to build the house? ................................................................................................................................................. 22. How can the skylights help us to save electricity? ................................................................................................................................................. 23. Why don‘t they use chemicals to clean the rooms? ................................................................................................................................................. 24. What can you see in the mountains? ................................................................................................................................................. 25. What are the activities for a boat trip? ................................................................................................................................................. Read the passage and choose the correct answer A, C, C or D (3pts) Rescue robots (26) _______________ hi-tech toys, but we are now using more robotic planes, helicopters. We can use them after storms, earthquakes, or fires to provide us with important (27) _______________. They have cameras and microphones that help rescue workers understand how much damage (28)_______________ and (29) _______________ where the victims are. These planes work (30)_______________ between 30 and 120 metres in the air and they can rescue people in somewhere very dangerous. 26. A. look B. look like C. looks like D. look at 27. A. information B. newspaper C. ideas D. thing 28. A. there B. it was C. there has D. there is 29. A. find B. find out C. finds D. finds out 30. A. much B. more C. the best D. best Rewrite the sentences starting with the given words. (5 pts) 31. Lan’s parents gave her a bike for her birthday. → Lan received ……………………………………………………………………... 32. It takes me about two hours each day to do my homework. → I spend …………………………………………………………………….... 33. Hoa is a hard student. → Hoa …………………………………………………………………….... 34. An drives dangerously. → An is …………………………………………………………………….... 35. How long have you bought this car? → When did ……………………………………………………………………... Reorder the words / phrases to complete the sentences. (3 pts) 36. music / like / the / I / evenings / listening / in / to. ................................................................................................................................................. 37. phone / she / me / the / not / at / weekend / will. ................................................................................................................................................. 38. soon / new / will / of / you / lots / have / friends. ................................................................................................................................................. Write full sentences using the given words. (2pts) 39. Lamp/ next/ the bed. ................................................................................................................................................. 40. Table/ the right/ the wardrobe. .................................................................................................................................................

9
9 tháng 7

tách nhỏ nhỏ ra cho dễ làm nha bạn, nhìn rối lắm :v

10 tháng 7

1. A. prefer B. better C. teacher D. worker

2. A. bear B. hear C. dear D. near

3. A. collect B. concern C. concert D. combine

Circle the odd one out. ( 2 points)

4. A. watches B. brushes C. teacher D. goes

5. A. meat B. fish C. beef D. tea 

a: ĐKXĐ: \(n\ne4\)

Để A là số nguyên thì \(3n+9⋮n-4\)

=>\(3n-12+21⋮n-4\)

=>\(21⋮n-4\)

=>\(n-4\in\left\{1;-1;3;-3;7;-7;21;-21\right\}\)

=>\(n\in\left\{5;3;7;1;11;-3;25;-17\right\}\)

b: ĐKXĐ: \(n\ne\dfrac{1}{2}\)

Để B là số nguyên thì \(6n+5⋮2n-1\)

=>\(6n-3+8⋮2n-1\)

=>\(8⋮2n-1\)

=>\(2n-1\in\left\{1;-1;2;-2;4;-4;8;-8\right\}\)

mà 2n-1 lẻ(do n là số nguyên)

nên \(2n-1\in\left\{1;-1\right\}\)

=>\(n\in\left\{1;0\right\}\)

1

Bài 3:

Gọi số cần tìm là x

Theo đề, ta có: -2x+3=-7-x

=>-2x+3=-x-7

=>-2x+x=-7-3

=>-x=-10

=>x=10

vậy: Số cần tìm là 10

Bài 1:

a: -100<x<0

mà x là số có chữ số tận cùng là 0

nên \(x\in\left\{-10;-20;-30;...;-90\right\}\)

Số số hạng là \(\dfrac{\left(-90+10\right)}{-10}+1=\dfrac{-80}{-10}+1=9\left(số\right)\)

Tổng của dãy số là \(\left(-90-10\right)\cdot\dfrac{9}{2}=-100\cdot\dfrac{9}{2}=-450\)

b: -12<=x<=20

mà x chia hết cho 5

nên \(x\in\left\{-10;-5;0;5;10;15;20\right\}\)

Tổng của dãy số là:

(-10)+(-5)+0+5+10+15+20

=(-10+10)+(-5+5)+0+15+20

=0+0+0+35

=35

c: -22<=x<14

mà x chia hết cho 9

nên \(x\in\left\{-18;-9;0;9\right\}\)

Tổng của dãy số là:

(-18)+(-9)+0+9

=(-18+0)+(-9+9)

=-18+0=-18

 

 

8 tháng 7

Chu vi tam giác đó là:

\(47+30+26=103\left(cm\right)\)

Diện tích tam giác đó là:

\(26\times13:2=169\left(cm^2\right)\)