Bài 3: sắp xếp các phân số sau thứ tự lớn đến bé: 15/16,3/2,21/32,5/8
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NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
25 tháng 3
1 x 4 + 2 x 5 + 3 x 6 + 47 x 50
= 4 + 10 + 18 + 2350
= (4 + 10) + (18 + 2350)
= 14 + 2368
= 2382
NV
Nguyễn Việt Dũng
CTVVIP
25 tháng 3
1. Afghanistan
2. Albania
3. Algeria
4. Andorra
5. Angola
6. Argentina
7. Armenia
8. Australia
9. Austria
10. Azerbaijan
11. Bahrain
12. Bangladesh
13. Barbados
14. Belarus
15. Belgium
16. Belize
17. Benin
18. Bhutan
19. Bolivia
20. Bosnia và Herzegovina
21. Botswana
22. Brazil
23. Brunei
24. Bulgaria
25. Burkina Faso
26. Burundi
27. Cabo Verde
28. Campuchia
29. Cameroon
30. Canada
31. Chad
32. Chile
33. Colombia
34. Comoros
35. Congo
36. Costa Rica
37. Croatia
38. Cuba
39. Cyprus
40. Cộng hòa Séc
30 tháng 3
- ý
- pháp
- anh
- đức
- mỹ
- úc
- ấn độ
- mianma
- bồ đào nha
- việt nam
- tây ban nha
- áo
- brazil
- thái lan
- xin-ga-bo
- thổ nhĩ kì
- bru-nây
- in-đô-nê-si-a
- lào
- cam pu chia
- malaysia
- nhật bản
- mông cổ
- trung quốc
- triều tiên
- hàn quốc
- đông ti mo
- nga
- ukraine
- romania
- bulgaria
- đan mạch
- ba lan
- hy lạp
- bỉ
- hà lan
- phần lan
- cộng hoà séc
- síp
- thuỵ điển
- canada
AH
Akai Haruma
Giáo viên
25 tháng 3
Lời giải:
$x^3+x^2+x+1=2^y$
$\Rightarrow x^2(x+1)+(x+1)=2^y$
$\Rightarrow (x+1)(x^2+1)=2^y$
$\Rightarrow x+1=2^m; x^2+1=2^n$ với $m,n$ là số tự nhiên, $m+n=y$
$\Rightarrow (2^m-1)^2+1=2^n$
$\Rightarrow 2^{2m}-2^{m+1}+2=2^n$
Nếu $m,n$ đều $\geq 2$ thì hiển nhiên $2=2^n+2^{m+1}-2^{2m}\vdots 4$ (vô lý)
$\Rightarrow$ tồn tại ít nhất 1 trong 2 số nhỏ hơn 2.
Giả sử $n<2$. Khi đó $n=0$ hoặc $n=1$.
+ Nếu $n=0$ thì $x=0\Rightarrow m=0\Rightarrow y=m+n=0$ (tm)
+ Nếu $n=1$ thì $x=1\Rightarrow m=1\Rightarrow y=m+n=2$ (tm)
TN
1
24 tháng 3
\(A=\dfrac{4}{15\cdot19}+\dfrac{4}{19\cdot23}+...+\dfrac{4}{399\cdot403}\)
\(=\dfrac{1}{15}-\dfrac{1}{19}+\dfrac{1}{19}-\dfrac{1}{23}+...+\dfrac{1}{399}-\dfrac{1}{403}\)
\(=\dfrac{1}{15}-\dfrac{1}{403}=\dfrac{403-15}{403\cdot15}=\dfrac{388}{6045}\)
\(\dfrac{16}{81}=\dfrac{16\cdot24,25}{81\cdot24,25}=\dfrac{388}{1964,25}\)
\(\dfrac{16}{80}=\dfrac{16\cdot24,25}{80\cdot24,25}=\dfrac{388}{1940}\)
Vì 1940<1964,25<6045
nên \(\dfrac{16}{80}>\dfrac{16}{81}>A\)
SV
Sinh Viên NEU
CTVVIP
24 tháng 3
1. She is good ______________ meteorology.
A. on B. in C. at D. for
2. Last night, volcano Maui ______________ and the large areas of land were affected.
A. erupts B. erupted C. erupting D. erupt
3. I _______ buy things online, just once or twice a year. I prefer to shop at the shopping mall.
A. rarely B. always C. usually D. often
4. My sister _______ watches the Junior Master Chef programme. She never misses an episode.
A. seldom B. never C. rarely D. always
5. People go to a shopping centre for many ______.
A. people B. thing C. reasons D. product
6. Con Dao National Park plays a key role in saving the ______.
A. small islands B. environment B. water D. air
7. She’s a _______. She spends too much time and money shopping.
A. worker B. student C. shopaholic D. farmer
8. A ______________ often occurs in the mountainous areas because many trees have been cut down.
A. forest fire B. flood C. tornado D. landslide
9. When there is a _______ , hot gases and liquid rock pour out from a mouuntain.
A. tornado B. storm C. earthquake D. volcanic eruption
10. People enjoy ______ for one or two hours in clean and well-lit areas.
A. walking B. walk C. have D. having
SV
Sinh Viên NEU
CTVVIP
24 tháng 3
11. They ______________ on the lake when it started to rain, so they went home.
A. fished B. fishing C. were fishing D. are fishing
12. Her dad found some money while he ______________ her suitcase.
A.packing B. package C. are packing D. was packing
13. Your brother ______________ in Myanma when he met his girlfriend.
A. study B. was studying C. were study D. was study
14. Ba: Were you having dinner at 6 p.m yesterday?
Nam: _______
A: No, I didn’t . C: Yes, I was.
B: Yes, I did. D: No, I don’t.
15. Her mom ______________ in the park when she saw a rabbit.
A. was going B. was going C. were going D. were going
16. _______it _______ when you woke up this morning?
A.Is...raining B. Was...raining C. Is...rain D.Were.. . rainin
17. What ______________ when his mother came?
A. were you doing B. was you doing C. are you doing D. are you doing
18. Don’t forget to turn off the lights ____ you go out.
A. after B. before C. till D. until
19. He ______ a sandwich when his phone rang.
A. is eating B. eats C. was eating D. ate
20. It ______________ when I left Ireland.
A. was rain B. was raining C. is raining D. raining
24 tháng 3
1,2m=12dm
Thể tích bể hiện tại là:
\(12^3\cdot\dfrac{3}{4}=1296\left(lít\right)\)
Thể tích nước còn lại trong bể sau khi dùng 4/9 lượng nước là:
\(1296\left(1-\dfrac{4}{9}\right)=720\left(lít\right)\)
\(\dfrac{15}{16}=\dfrac{15\cdot2}{16\cdot2}=\dfrac{30}{32};\dfrac{3}{2}=\dfrac{3\cdot16}{2\cdot16}=\dfrac{48}{16};\dfrac{21}{32}=\dfrac{21}{32};\dfrac{5}{8}=\dfrac{5\cdot4}{8\cdot4}=\dfrac{20}{32}\)
mà 48>30>21>20
nên \(\dfrac{3}{2}>\dfrac{15}{16}>\dfrac{21}{32}>\dfrac{5}{8}\)
3/2 > 15/16 > 21/32 > 5/8