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6 tháng 6 2024

*) Với ba chữ số: 0; 1; 2, ta lập được các số:

102; 120; 201; 210

*) Với ba chữ số: 0; 1; 5 ta lập được các số sau:

105; 150; 501; 510

*) Với ba chữ số: 0; 2; 4 ta lập được các số sau:

204; 240; 402; 420

*) Với ba chữ số: 0; 3; 6 ta lập được các số sau:

306; 360; 603; 630

*) Với ba chữ số: 1; 2; 3 ta lập được các số sau:

123; 132; 213; 231; 312; 321

*) Với ba chữ số: 1; 2; 6 ta lập được các số sau:

126; 162; 216; 261; 612; 621

*) Với ba chữ số: 2; 4; 6 ta lập được các số sau:

246; 264; 426; 462; 624; 642

Vậy số các số có thể lập được là:

4 + 4 + 4 + 4 + 6 + 6 + 6 = 34 (số)

3 tháng 6 2024

Chọn A

Đặt (d): ax+by-9=0

Tọa độ điểm A là: \(\begin{cases}y=0\\ ax-9=0\end{cases}\Rightarrow\begin{cases}y=0\\ x=\frac{9}{a}\end{cases}\)

=>\(OA=\sqrt{\left(\frac{9}{a}-0\right)^2+\left(0-0\right)^2}=\sqrt{\left(\frac{9}{a}\right)^2}=\frac{9}{\left|a\right|}\)

Tọa độ điểm B là: \(\begin{cases}x=0\\ by-9=0\end{cases}\Rightarrow\begin{cases}x=0\\ by=9\end{cases}\Rightarrow\begin{cases}x=0\\ y=\frac{9}{b}\end{cases}\)

=>\(OB=\sqrt{\left(0-0\right)^2+\left(\frac{9}{b}-0\right)^2}=\sqrt{\left(\frac{9}{b}\right)^2}=\frac{9}{\left|b\right|}\)

OA=2OB

=>\(\frac{9}{\left|a\right|}=2\cdot\frac{9}{\left|b\right|}=\frac{18}{\left|b\right|}\)

=>18|a|=9|b|

=>|b|=2|a|

=>b=2a hoặc b=-2a

(C): \(\left(x-2\right)^2+\left(y-1\right)^2=5\)

=>tâm là I(2;1) và bán kính là \(R=\sqrt5\)

Vì (d) là tiếp tuyến của (C) nên \(d\left(I;\left(d\right)\right)=R=\sqrt5\)

=>\(\frac{\left|2\cdot a+1\cdot b-9\right|}{\sqrt{a^2+b^2}}=\sqrt5\)

=>\(\left|2a+b-9\right|=\sqrt{5\left(a^2+b^2\right)}\)

=>\(5\left(a^2+b^2\right)=\left(2a+b-9\right)^2\) (1)

Th1: b=2a

(1) sẽ trở thành: \(5\left\lbrack a^2+\left(2a\right)^2\right\rbrack=\left(2a+2a-9\right)^2=\left(4a-9\right)^2\)

=>\(5\cdot5a^2=\left(4a-9\right)^2\)

=>\(\left(5a\right)^2-\left(4a-9\right)^2=0\)

=>(5a-4a+9)(5a+4a-9)=0

=>\(\left[\begin{array}{l}a+9=0\\ 9a-9=0\end{array}\right.\Rightarrow\left[\begin{array}{l}a=-9\\ a=1\end{array}\right.\)
Khi a=-9 thì b=2a=-18

Khi a=1 thì b=2a=2

TH2: b=-2a

(1) sẽ trở thành:

\(5\left\lbrack a^2+\left(-2a\right)^2\right\rbrack=\left(2a-2a-9\right)^2\)

=>\(5\left(a^2+4a^2\right)=\left(-9\right)^2\)

=>\(5\cdot5a^2=81\)

=>\(25a^2=81\)

=>\(a^2=\frac{81}{25}\)

=>\(\left[\begin{array}{l}a=\frac95\left(loại\right)\\ a=-\frac95\left(loại\right)\end{array}\right.\)

Khi a=-9 và b=-18 thì a+2b=-9-36=-45

Khi a=1 và b=2 thì a+2b=1+4=5

Frederick Pohl Frederick Pohl’s book flits light-heartedly from continent to continent, mixing travelogue with gentle scientific explanation. This unusual (1) …… gives Mr Pohl the freedom to (2) …… into an extraordinarily diverse range of topics, including the physics of rainbows, and how to search for fossils in the marbled halls of downtown banks. It is all good fun, yet among the anecdotes and curious facts the scientific content is deceptively (3) …… . And along the way Mr...
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Frederick Pohl Frederick Pohl’s book flits light-heartedly from continent to continent, mixing travelogue with gentle scientific explanation. This unusual (1) …… gives Mr Pohl the freedom to (2) …… into an extraordinarily diverse range of topics, including the physics of rainbows, and how to search for fossils in the marbled halls of downtown banks. It is all good fun, yet among the anecdotes and curious facts the scientific content is deceptively (3) …… . And along the way Mr Pohl makes a serious point. (4) …… it is not necessary to be an athlete to enjoy sport, his book suggests, it is not necessary to be a scientific expert to (5) …… science. By pointing out where science is most apparent in the world, Mr Pohl entertainingly demonstrates that it is not some (6) …… activity, but is instead everywhere that science is, in the end, a world view. 1 A accent B approa ch C manner D mea ns 2 A delve B rumma ge C investig ate D expl ore 3 A consider able B grand C ample D high 4 A Just as B Beside s C Wherea s D Even if 5 A attain B appreci ate Cappeal D ende ar 6 A abject B obsolet e C arcane D obtuse

Giúp mik vs ạ , mik đang cần gấp

 

1
29 tháng 5 2024

1. C. manner

2. D. explore

3. A. considerable

4. A. Just as

5. B. appreciate

6. C. arcane

4 tháng 6 2024

def count_multiples_of_3(n):
    return n // 3
n = int(input())
result = count_multiples_of_3(n)
print(result)

28 tháng 5 2024

1. C

2. D

3. C

4. D

5. B

6. C

7. A

8. B

9. B

10. D

AH
Akai Haruma
Giáo viên
28 tháng 5 2024

Biểu thức mẫu là $\sqrt{4}-x^2$ hay $\sqrt{4-x^2}$ vậy bạn?

A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 34 to 40 Some Russian women became well-known fighter pilots during the Second World War. Yekaterina Budanova was one of them. She joined the Soviet Army and became a lighter pilot after working as a non-military pilot. At first, Budanova's officer didn't believe in her ability. But in a short time Budanova became famous for her talent and remarkable flying skills. Unfortunately, she died at the...
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A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 34 to 40

Some Russian women became well-known fighter pilots during the Second World War. Yekaterina Budanova was one of them. She joined the Soviet Army and became a lighter pilot after working as a non-military pilot. At first, Budanova's officer didn't believe in her ability. But in a short time Budanova became famous for her talent and remarkable flying skills. Unfortunately, she died at the age of 26 in air-to-air fighting against German planes although she already shot down one plane and hit a second before being shot down herself.

 Interested in flying at an early age, Lydia Ultvyak joined a flying club and performed her first solo flight at the age of 15. She became a fight instructor after graduating from the military flying school. After the German attack on the Soviet Union in 1941. Utvyak joined the Soviet Air Force and soon achieved great success. Like Budanova, she was killed (at the age of 21) in fighting against German planes. And along with Yekaterina Budanova Lydia Utvyak is often considered one of the world's most famous female fighter pilots.

 

Question 34. Which of the following best serves as the title of the text?

       A. Russian Female Fighter Pilots                             B. Female Fighter Pilots Who Made History

       C. Women during the Second World War               D. Fighting the Germans

 Question 35. The fact that Litvyak had her first solo flight when she was only 15 implies that __________.

       A. it was a risky thing to do                                     B. she loved danger

       C. she had a natural talent for flying                        D. her flying club was the best in the world

 Question 36. What did Budanova do before she become a fighter pilot?

       A. She worked at a flying club.                                B. She was a Russian officer.

       C. She worked as a non-military pilot.                    D. She shot down German planes.

 Question 37. The word 'solo' in paragraph 2 is opposite meaning to ________.

       A. done by one person alone                                    B. successful                                             

       C. done by more than one person                             D. single

 Question 38. The phrase "a second" in paragraph 1 refers to _______.

       A. the Second World War                                                                                B. a second German plane          

       C. a second Russian plane                                       D. a fighter pilot

 Question 39. The word "them" in paragraph 1 refers to_______.

       A. fighter pilots                                                        B. well-known fighter pilots

       C. some Russian women                                          D. women    

 Question 40. Which of the following is NOT true about Budanova and Uitvyak, according to the text?

       A. They died in their twenties.

       B. They died when the Second World War was over.

       C. They were talented and successful female fighter pilots in the Soviet Air Force.

       D. They are considered two of the world's most famous female fighter pilots.

2
24 tháng 5 2024

34. B

35. C

36. C

37. A

38. C

39. C

40. B

24 tháng 5 2024

Question 34. Which of the following best serves as the title of the text?

       A. Russian Female Fighter Pilots                             B. Female Fighter Pilots Who Made History

       C. Women during the Second World War               D. Fighting the Germans

 Question 35. The fact that Litvyak had her first solo flight when she was only 15 implies that __________.

       A. it was a risky thing to do                                     B. she loved danger

       C. she had a natural talent for flying                        D. her flying club was the best in the world

 Question 36. What did Budanova do before she become a fighter pilot?

       A. She worked at a flying club.                                B. She was a Russian officer.

       C. She worked as a non-military pilot.                    D. She shot down German planes.

 Question 37. The word 'solo' in paragraph 2 is opposite meaning to ________.

       A. done by one person alone                                    B. successful                                             

       C. done by more than one person                             D. single

 Question 38. The phrase "a second" in paragraph 1 refers to _______.

       A. the Second World War                                                                                B. a second German plane          

       C. a second Russian plane                                       D. a fighter pilot

 Question 39. The word "them" in paragraph 1 refers to_______.

       A. fighter pilots                                                        B. well-known fighter pilots

       C. some Russian women                                          D. women    

 Question 40. Which of the following is NOT true about Budanova and Uitvyak, according to the text?

       A. They died in their twenties.

       B. They died when the Second World War was over.

       C. They were talented and successful female fighter pilots in the Soviet Air Force.

       D. They are considered two of the world's most famous female fighter pilots.

23 tháng 5 2024