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\(A=\frac{1}{3}.\left(\frac{3}{2.4.6}+\frac{3}{4.6.8}+...+\frac{3}{22.24.26}\right)\)
\(A=\frac{1}{3}.\left(\frac{1}{2.4}-\frac{1}{4.6}+\frac{1}{4.6}-\frac{1}{6.8}+...+\frac{1}{22.24}-\frac{1}{24.26}\right)\)
\(A=\frac{1}{3}.\left(\frac{1}{2.4}-\frac{1}{24.26}\right)\)
\(A=\frac{1}{3}.\frac{77}{624}\)
\(A=\frac{77}{1872}\)

Nhớ rằng: \(\frac{n}{a.\left(a+n\right)}=\frac{1}{a}+\frac{1}{a+n}\)
Ta có: \(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{90}\)
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}\)
Áp dụng công thức trên, ta có:
\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\)
\(A=1-\frac{1}{10}=\frac{9}{10}\)

Odd one out
1. A.scarf B.sandals C.boots D.shoes
2. A.soccer B.tennis C.badminton D.sport
3. A.elephant B.animal C.dolphin D.shark
4. A.play B.seafood C.sandcastle D.beach ball
5.A.violin B.guitar C.music D.piano
6. A.football B.table tennis C.volleyball D.play
7. A.music B.english C.books D.physics
8. A. party B. invite C. complete D. money câu này chịu
9. A.flowers B. visit C. clothes D.sport câu này chịu
10. A. their B. me C. his D. our
11. A. coat B. sandals C. boots D. shoes
11.A.cycle B.ski C.skate D.chess
12.A. giraffe B. seafood C. dolphin D. shark
13.A.play B. badminton C.football D. chess
14. A.english B.music C.subject D.history
nếu sai cho mình xin lỗi
1. A.scarf B.sandals C.boots D.shoes
2. A.soccer B.tennis C.badminton D.sport
3. A.elephant B.animal C.dolphin D.shark
4. A.play B.seafood C.sandcastle D.beach ball
5.A.violin B.guitar C.music D.piano
6. A.football B.table tennis C.volleyball D.play
7. A.music B.english C.books D.physics
8. A. party B. invite C. complete D. money
9. A.flowers B. visit C. clothes D.sport
10. A. their B. me C. his D. our
11. A. coat B. sandals C. boots D. shoes
11.A.cycle B.ski C.skate D.chess
12.A. giraffe B. seafood C. dolphin D. shark
13.A.play B. badminton C.football D. chess
14. A.english B.music C.subject D.history

1. Where do your mother often buy this book? => Where does your mother often buy this book?
2. Are Tom studying? => Is Tom studying?
3. Hoa not have good speaking skill. => Hoa does not have good speaking skill
4. The young girl not writing the letter now. => The young girl is not writing the letter now.
5. Are Lam fond of listening music?=> Is Lam fond of listening to music?
6. They studies math=> They study math
7. What you usually do in the morning? => What do you usually do in the morning?
8. They are traveling to London. => Th ey are travelling to London.
9. The plane is land now.=> The plane is landing now
10. Why she is saying loudly?=> Why is she saying loudly?
1. Where do your mother often buy this book?
=> Where does your mother often buy this book?
2. Are Tom studying English now?
=>Is tom studying English now?
3. Hoa not have good speaking skill.
=>Hoa doesn't have good speaking skill.
4. The young girl not writing the letter now.
=> That young girl isn't writing the letter now.
5. Are Lam fond of listening music?
=> Does Lam fond of listening to music?
6. They studies math once time a week.
=> They study math once time a week.
7. What you usually do in the morning?
=> What do you usually do in the morning?
8. They are traveling to London.
=>They are travelling to London.
9. The plane is land now.
=> The plane is landing now.
10. Why she is saying loudly?
=> why is she saying loudly?
Hok tốt

Bài nghe:
1. How can I get to the bookshop?
(Làm thế nào để tôi có thể đến hiệu sách?)
2. How can I get to the campsite?
(Làm thế nào để tôi có thể đến khu cắm trại?)
Lời giải chi tiết:
1. c 2. a

a.
What are these animals? (Đây là những con vật gì?)
They’re peacocks. (Chúng là những con công.)
I like them. (Tôi thích chúng.)
b.
Why do you like peacocks? (Vì sao bạn thích con công?)
Because they dance beautifully. (Bởi vì chúng múa rất đẹp.)

a.
What does your mother do? (Mẹ bạn làm nghề gì vậy?)
She’s a nurse. (Bà ấy là y tá.)
b.
Where does she work? (Bà ấy làm việc ở đâu?)
She works at a nursing home. (Bà ấy làm việc ở viện dưỡng lão.)

Bài nghe:
1. A: What does your mother do? (Mẹ bạn làm nghề gì?)
B: She's a farmer. (Bà ấy là một nông dân.)
2. A: What does your father do? (Bố bạn làm nghề gì?)
B. He's a policeman. (Ông ấy là một cảnh sát.)
3. A: Is your mother an office worker? (Mẹ bạn có phải là một nhân viên văn phòng không?)
B: Yes, she is. (Đúng vậy.)
4. A: What does your father do? (Bố bạn làm nghề gì?)
B: He's a farmer. (Ông ấy là một nông dân.)
Lời giải chi tiết:
1. ✕ | 2. ✓ | 3. ✓ | 4. ✕ |

a.
How old is your father, Mai? (Bố của Mai bao nhiêu tuổi rồi?)
He’s forty. (Ông ấy 40 tuổi.)
b.
What does he look like? (Ông ấy trông như thế nào?)
He has a round face. (Ông ấy có khuôn mặt tròn.)
3
1+1=2