A=21+22+23+.....+21010
Help me!!!!!!!!!!!!!!!!!!!!!!!!!
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NN
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9 tháng 11 2021
19. Maryam was really impressed __by______ the beauty of Hue.
20. It seems difficult ____for____ me to meet her now.
21. He doesn’t depend ____on_____ his parents.
22. If you have any trouble, ask ____for____ help.
23. This guidebook is full ____of___ useful information.
24. We still keep in touch ____with____ each other although we live away ___with____ each other.
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26. She went out __without______ saying a word.
27. What do you often do ____at____ the weekends?
28. She was born _____on___ 15th September..
S
9 tháng 11 2021
19. Maryam was really impressed _by_______ the beauty of Hue.
20. It seems difficult __for______ me to meet her now.
21. He doesn’t depend ____on____ his parents.
22. If you have any trouble, ask ___for_____ help.
23. This guidebook is full ___of_____ useful information.
24. We still keep in touch ___with_____ each other although we live away ____from____ each other.
25. He will go to China ____at____ the end ___of_____ this week.
26. She went out _without_______ saying a word.
27. What do you often do ____at____ the weekends?
28. She was born ____on____ 15th September..
NN
2
BD
5 tháng 8 2023
\(A=2^{100}-2^{99}+2^{98}-2^{97}+....-2^3+2^2-2+1\\ A=\left(2^{100}+2^{98}+...+2\right)-\left(2^{99}+2^{97}+...+1\right)\)
Gọi \(\left(2^{100}+2^{98}+...+2\right)\)là B
\(B=\left(2^{100}+2^{98}+...+2\right)\\ 2B=2^{102}+2^{100}+.....+2^2\\ 2B-B=\left(2^{102}+2^{100}+.....+2^2\right)-\left(2^{100}+2^{98}+...+2\right)\\ B=2^{102}-2\)
Gọi \(\left(2^{99}+2^{97}+...+1\right)\) là C
\(C=\left(2^{99}+2^{97}+...+1\right)\\ 2C=2^{101}+2^{99}+....+2\\ 2C-C=\left(2^{101}+2^{99}+9^{97}+...+2\right)-\left(2^{99}+9^{97}+...+1\right)\\ C=2^{101}-1\)
\(A=B+C\\ =>A=2^{102}-2+2^{101}-1\\ A=2^{101}\left(2+1\right)-3\\ A=2^{101}\cdot3-3\\ A=3\cdot\left(2^{101}-1\right)\)
HQ
Hà Quang Minh
Giáo viên
5 tháng 8 2023
\(\dfrac{1}{2}A=2^{99}-2^{98}+...-1+\dfrac{1}{2}\\ \Rightarrow A-\dfrac{1}{2}A=2^{100}-\dfrac{1}{2}\\ \Rightarrow A=2^{101}-1\)
NN
1
DT
Đỗ Thanh Hải
CTVVIP
5 tháng 6 2021
* Chuyển các câu sau từ câu trực tiếp sang gián tiếp.
21. “ Hurry up, Lan!”.
He told Lan......to hurry up...................................
22 .“ I feel like going to America soon”.
The woman looked forward to …going to America soon……………….....
23. “ It’s really nice of you to help me”, Peter said to Jack.
Peter thanked…Jack……….for …helping him………….............
24.“ Don’t play games on computer all day”, Tom’s mother said to him.
Tom’s mother warned …him…..against ..playing games on computer all day.....................................
25.“ I hear you passed your driving test.Congratulation!”, Peter said to me.
Peter congratulated …me……. on …passing my driving test……............................
26.“ I’m sory. I didn’t do my homework,” John said to his English teacher.
John apologised ……to his English teacher……...for ……not doing his homework……............................
27.“ I always want to become an English teacher,” Mary said.
Mary dreamed of …becoming an English teacher………………………
28.He said , ‘ This house was built in 1980”.
He said .....this house had been built in 1980...............................
29.“ Will Tom be here tomorrow?”.
She wondered ..if Tom would be there the following day.......................................
30.“ Please don’t smoke in my car”
He asked his friend.....not to smoke in his car...................
MN
5 tháng 6 2021
21. “ Hurry up, Lan!”.
He told Lan.............. to hurry up...........................
22 .“ I feel like going to America soon”.
The woman looked forward to ………. going to America soon………….....
23. “ It’s really nice of you to help me”, Peter said to Jack.
Peter thanked…Jack……….for ………helping him…….............
24.“ Don’t play games on computer all day”, Tom’s mother said to him.
Tom’s mother warned …him…..against ..........playing games on computer all day.............................
25.“ I hear you passed your driving test.Congratulation!”, Peter said to me.
Peter congratulated …me……. on ………...passing my driving test.........................
26.“ I’m sory. I didn’t do my homework,” John said to his English teacher.
John apologised ……his English teacher……...for ………not doing his homework…............................
27.“ I always want to become an English teacher,” Mary said.
Mary dreamed of ………being an English teacher…………………
28.He said , ‘ This house was built in 1980”.
He said .............this house had been built in 1980.......................
29.“ Will Tom be here tomorrow?”.
She wondered ..................if Tom would be there the following day........................
30.“ Please don’t smoke in my car”
He asked his friend......not to smoke in his car..................
7 tháng 11 2021
\(A=\left(1+2\right)+2^2\left(1+2\right)+...+2^{10}\left(1+2\right)=3+2^2.3+...+2^{10}.3=3\left(1+2^2+...+2^{10}\right)⋮3\)
NT
2
KV
11 tháng 7 2023
\(A=\dfrac{21}{22}+\dfrac{22}{23}=\dfrac{967}{506}>1\)
\(B=\dfrac{21+22}{22+23}=\dfrac{43}{45}< 1\)
Vậy \(A>B\)
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
11 tháng 7 2023
\(\dfrac{21}{22}\) > \(\dfrac{21}{22+23}\)
\(\dfrac{22}{23}\) > \(\dfrac{22}{22+23}\)
Cộng vế với vế ta có:
A = \(\dfrac{21}{22}\) + \(\dfrac{22}{23}\) > \(\dfrac{21+22}{22+23}\) = B ⇒ A > B
QT
1
NA
26 tháng 12 2021
a) 23 + (-77) + (-23) + 77 =
[23 + (-23)] + [(-77) + 77]
= …0+0=0……
b) (-2 020) + 2 021 + 21 + (-22)
=[(-2 020) + 2 021] + [21 + (-22)]
= …1……+ (-1)……..
= 0.
=> 2A = 22+23+24+...+21011
=> 2A - A = (22+23+24+...+21011) - (21+22+23+...+21010)
=> A = 21011-2.
~ HỌC TỐT NHÁ
A = 2 + 22 + 23 + ... + 22010
2A = 22 + 23 + 24 + ... + 22011
2A - A = 22011 - 2