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NB
6
30 tháng 4 2016
Bạn xem lời giải của mình nhé:
Giải:
\(S=\frac{1}{5}+\left(\frac{1}{13}+\frac{1}{14}+\frac{1}{15}\right)+\left(\frac{1}{61}+\frac{1}{62}+\frac{1}{63}\right)\\ \frac{1}{13}< \frac{1}{12}\\ \frac{1}{14}< \frac{1}{12}\\ \frac{1}{15}< \frac{1}{12}\\ \frac{1}{61}< \frac{1}{60}\\ \frac{1}{62}< \frac{1}{60}\\ \frac{1}{63}< \frac{1}{60}\)
\(\Rightarrow\frac{1}{5}+\left(\frac{1}{13}+\frac{1}{14}+\frac{1}{15}\right)+\left(\frac{1}{61}+\frac{1}{62}+\frac{1}{63}\right)< \frac{1}{5}+\left(\frac{1}{12}+\frac{1}{12}+\frac{1}{12}\right)+\left(\frac{1}{60}+\frac{1}{60}+\frac{1}{60}\right)\)
\(\Rightarrow A< \frac{1}{5}+\frac{1}{12}.3+\frac{1}{60}.3\\ \Rightarrow A< \frac{1}{5}+\frac{1}{4}+\frac{1}{20}\\ \Rightarrow A< \frac{4+5+1}{20}\\ \Rightarrow A< \frac{1}{2}\left(đpcm\right)\)
Chúc bạn học tốt!
PA
1
ND
21 tháng 9 2020
1. There will be a beautiful place.
There will not be a beautiful place.
Will be a beautiful place?
2. There will have a lot of pupils.
There will not have a lot of pupils.
Will have a lot of pupils?
KY
22 tháng 7 2019
a.Em hãy chọn đáp án đúng A,B hoặc C để điền vòa các câu sau.
1.My brother ..........to buy a new car.
| A.want | B.wants | C.to want |
2.Some Canadians ..........English and french.
| A.speak | B.speaks | C.to speak |
3.Tuesday ..........a very long day for me.
| A.is | B.are | C.to be |
4.The teacher ..........French ang English.
| A.know | B.knows | C.to know |
5.Greek and Chinese ..........dificult languages to learn.
| A.is | B.are | C.be |
6.A trip from here to London ..........about 7 hours.
| A.take | B.takes | C.to take |
7.Tomorrow's homework ..........on page 37.
| A.begin | B.begins | C.began |
8.Thers is ............traffie jam along the expressway.
| A.a | B.an | C.the |
9.Mother left ...........house without her keý.
| A.a | B.an | C.the |
10.Mother prepares ...........sandwíches and ...........milk for out breakfast.
| A.a/x | B.x/x | C.the/a |
11............author is someone who writes books.
| A.a | B.an | C.the |
12.I have ............uncle who teachers at Chu Van An Primary School.
| A.a | B.an | C.the |
13.There are many ..........fish.
| A.a | B.an | C.x |
14.Nam has ...........orange.He wants to share with his younger brother.
| A.a | B.an | C.the |
15.Do you swim in ...........sea every day in ...........summer?
| A.a/the | B.the/x | C.the/the |
16.My father is ..........farmer.He works hard in ..........field.
| A.a/the | B.a/a | C.the/the |
17John lives in ..........city with his mother,father and sister.He doessn't like ..........noise.He wishes to move to ..........countrýide to enjoy fresh air.
| A.a/the/a | B.the/the/the | C.the/x/the |
KY
22 tháng 7 2019
a.Em hãy chọn đáp án đúng A,B hoặc C để điền vòa các câu sau.
1.My brother ..........to buy a new car.
| A.want | B.wants | C.to want |
2.Some Canadians ..........English and french.
| A.speak | B.speaks | C.to speak |
3.Tuesday ..........a very long day for me.
| A.is | B.are | C.to be |
4.The teacher ..........French ang English.
| A.know | B.knows | C.to know |
5.Greek and Chinese ..........dificult languages to learn.
| A.is | B.are | C.be |
6.A trip from here to London ..........about 7 hours.
| A.take | B.takes | C.to take |
7.Tomorrow's homework ..........on page 37.
| A.begin | B.begins | C.began |
8.Thers is ............traffie jam along the expressway.
| A.a | B.an | C.the |
9.Mother left ...........house without her keý.
| A.a | B.an | C.the |
10.Mother prepares ...........sandwíches and ...........milk for out breakfast.
| A.a/x | B.x/x | C.the/a |
11............author is someone who writes books.
| A.a | B.an | C.the |
12.I have ............uncle who teachers at Chu Van An Primary School.
| A.a | B.an | C.the |
13.There are many ..........fish.
| A.a | B.an | C.x |
14.Nam has ...........orange.He wants to share with his younger brother.
| A.a | B.an | C.the |
15.Do you swim in ...........sea every day in ...........summer?
| A.a/the | B.the/x | C.the/the |
16.My father is ..........farmer.He works hard in ..........field.
| A.a/the | B.a/a | C.the/the |
17John lives in ..........city with his mother,father and sister.He doessn't like ..........noise.He wishes to move to ..........countrýide to enjoy fresh air.
| A.a/the/a | B.the/the/the | C.the/x/the |
19 tháng 4 2016
Bài 1 :
\(S=\frac{2}{1.2.3}+\frac{2}{2.3.4}+...+\frac{2}{2009.2010.2011}\)
\(=\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{2009.2010}-\frac{1}{2010.2011}\)
\(=\frac{1}{1.2}-\frac{1}{2010.2011}<\frac{1}{2}\)
Vậy \(S<\frac{1}{2}\)
Bài 2:
Làm nhiều rồi vào trong chỗ góc học tập của tớ mà coi 
LD
18 tháng 7 2017
1. What ................. you ............. in this dark room ?
| A. are .... do | B. are ...doing | C. are ... done | D. x.... do |
2. What did he ............. to her yesterday ?
| A. said | B. say | C. says | D. saying |
3. I ...................... . It's harmful.
| A. never smoke | B. am never smoke | C. smoke | D. smoking |
4. I like living in this street ...................... it is noisy.
| A. even though | B. despite | C. in spite of |
5. Hong's room is very dirty. Mine is much ...................... .
| A. clean | B. cleaner | C. cleaning |
6. The play was very boring. It's the .................. film I' ve ever seen.
| A. worst | B. best | C. good |
7. The children will be ............... if he teaches them English.
| A. happily | B. happiness | C. happy |
8. Water ....................... most of the Earth's surface.
| A. covers | B. cover | C. covered |
9. " Have a nice trip !" - " ........................... "
| A. Thanks | B. You're welcome | Goodbye |
HN
18 tháng 7 2017
1. What ................. you ............. in this dark room ?
| A. are .... do | B. are ...doing | C. are ... done | D. x.... do |
2. What did he ............. to her yesterday ?
| A. said | B. say | C. says | D. saying |
3. I ...................... . It's harmful.
| A. never smoke | B. am never smoke | C. smoke | D. smoking |
4. I like living in this street ...................... it is noisy.
| A. even though | B. despite | C. in spite of |
5. Hong's room is very dirty. Mine is much ...................... .
| A. clean | B. cleaner | C. cleaning |
6. The play was very boring. It's the .................. film I' ve ever seen.
| A. worst | B. best | C. good |
7. The children will be ............... if he teaches them English.
| A. happily | B. happiness | C. happy |
8. Water ....................... most of the Earth's surface.
| A. covers | B. cover | C. covered |
9. " Have a nice trip !" - " ........................... "
| A. Thanks | B. You're welcome | Goodbye |
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