\(\dfrac{4}{9\cdot11}+\dfrac{4}{11\cdot13}+...+\dfrac{4}{97\cdot99}\)

\(=2\left(\dfrac{2}{9\cdot11}+\dfrac{2}{11\cdot13}+...+\dfrac{2}{97\cdot99}\right)\)

\(=2\left(\dfrac{1}{9}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{13}+...+\dfrac{1}{97}-\dfrac{1}{99}\right)\)

\(=2\cdot\left(\dfrac{1}{9}-\dfrac{1}{99}\right)\)

\(=2\cdot\dfrac{10}{99}=\dfrac{20}{99}\)

1. Nam (never / eat) _____hasn't eaten__________ pizza before.
2. He (study) _______has studied_________ English for two hours every day.
3. Khoa (like) _____likes__________ omelette very much. It’s his favorite food.
4. My grandmother hates (eat) ____eating___________ noodles. She prefers rice.
5. Thanh (study) ________is studying_______ Physics at the moment.
6. I can’t sleep because the children (play) _______ play________ the drum in the living room.
7. I enjoy (fish) ___fishing____________ because it (be) ______is____________ relaxing.
8. I think, in the future people (not play) ____won't play____ individual games.
9. We find (arrange) ______arranging_________ flowers interesting because it (help) ______helps_________ us relax.
10. I (not collect) _______won't collect________ dolls when I grow up.
11. ______Have_________ Lan (do) _____done__________ her project yet?
12. ________Have_______ you ever (eat) ______eaten_________ Sushi?
13. We (go) _____went__________ to that village to do volunteer work last week.
14. Tom (call) ________called_______ his boss yesterday.
15. She often (go) ____Does she often___________ to the market with her mother once a week?
16. We (visit) ___are going to visit____________ Ha Noi next month.
17. Lan and her father (visit) _______visited________ the Temple of Literature 2 weeks ago.
18. They (not start) _______haven't started________ the project yet.
19. I (have read) _____have read__________ that novel by Hemingway several times.
20. I think in the future, people (explore) ______will explore_________ the nature in stead of watching T.V

câu 3 : kq 2 phần 3

câu 4 : kq -1

câu 5 : kq -8 phần 3

câu 6 : kq 4 phần 3 

câu 7 : kq -3

câu 9 : x = 1 phần 2

câu 10 : kq x =13 phần 12

câu 12 : 2 mũ 3 phần 3 mũ 3 = 8 phần 27

câu 13 : câu D nha

câu 10 ; 12 mình ko trắc lắm đâu nha

còn câu 8 mình ko rỏ mình sẻ tính lại sau

cau hoi nao ?

ừ, bạn viết ra đi

bạn có ra bài toán nào đâu mà bọn mình làm cho cậu ?

mà cậu có bài nào đâu mà bọn mình làm giúp cậu đúng không các bạn ?

uk đúng rùi, ra đè đê mà đây cũng ko bít làm đua

cậu gửi lại nhé