\(16\cdot18\cdot20\cdot22\)

\(=\left(17-1\right)\cdot\left(17+1\right)\cdot\left(21-1\right)\cdot\left(21+1\right)\)

\(=(17^2+17-17-1)\cdot\left(21^2+21-21-1\right)\)

\(=\left(17^2-1\right)\cdot\left(21^2-1\right)\)

\(=17^2\cdot21^2-17^2-21^2+1\)

\(=\left(19^2-72\right)\cdot\left(19^2+80\right)-17^2-21^2+1\)

\(=19^4+19^2\cdot80-72\cdot19^2-5760-17^2-21^2+1\)

\(=19^4+19^2\cdot\left(80-72\right)-5760-289-441+1\)

\(=19^4+19^2\cdot8-6489\)

\(=19^4+2888-6489\)

\(=19^4-3601\)

\(\Rightarrow19^4\cdot\cdot\cdot16\cdot18\cdot20\cdot22\)(>)

Tìm n biết:

a.9<3ⁿ <81

b.25\<5ⁿ \< 125

"\<" có nghĩa là lớn hơn hoặc bằng nhé

Mk đang cần rất gấp ai nhanh mk k 2 k

Ta có 19^4=130321

           16.18.20.22=126720

mà 130321 > 126720

nên 19^4 > 16.18.20.22

K NHA BẠN

Để 56x3y chia hết cho 2 thì y = 0;2;4;6;8

Nếu y = 0 thì 5 + 6 + x + 3 + 0 = 14 + x chia hết cho 9 thì x = 4

Nếu y = 2 thì 5 + 6 + x + 3 + 2 = 16 + x chia hết cho 9 thì x = 2

Nếu y = 4 thì 5 + 6 + x + 3 + 4 = 18 + x chia hết cho 9 thì x = 0 ; 9

Nếu y = 6 thì 5 + 6 + x + 3 + 6 = 20 + x chia hết cho 9 thì x = 7

Nếu y = 8 thì 5 + 6 + x + 3 + 8 = 22 + x chia hết cho 9 thì x = 5

56x38 chia hết 9 suy ra [5+6+x+3+8] chia hết 9 suy ra 22+x chia hết 9 suy ra x=5

Bài làm

Vì 56x3y chia hết cho 2

=>  \(y\in\left\{0;2;4;6;8\right\}\)

Mà 56x37 phải chia hết cho cả 9

=> 5 + 6 + x + 3 + 7 + y phải chia hết cho 9

thay y = 0 ta được: 5 + 6 + x + 3 + 7 + 0 chia hết cho 9

=> x = 6

Thay y = 2 ta được: 5 + 6 + x + 3 + 7 + 2 chia hết cho 9

=> x = 3

Thay y = 4 ta được: 5 + 6 + x + 3 + 7 + 4 chia hết cho 9

=> x = 2

Thay y = 6 ta được: 5 + 6 + x + 3 + 7 + 6 chia hết cho 9

=> x = 0

Thay y = 8 ta được: 5 + 6 + x + 3 + 7 + 8 chia hết cho 9

=> x = 7

Vậy \(x\in\left\{6;3;2;0;7\right\}\)

\(y\in\left\{0;2;4;6;8\right\}\)

Tham khảo

There is a famous animated film that I think everyone of us has seen at least once, and it is Tom and Jerry. Almost everyone is aware of the story between the miserable Tom and the mischievous mouse Jerry, and it also was part of my childhood memories. The film is about a life under the same roof between two enemies Tom and Jerry, and of course cat and mouse are always hard to get along with. Tom's owner is very afraid mouse, so she always asks Tom to catch the little mouse living in a cave that he digs on the wall. Tom is a quite lazy cat, and he often has to chase Tom so that he is not scolded by his owner or in exchange for a good meal. Sometimes, Jerry also makes mischievous jokes to tease Tom such as pull out his hair or steal his milk. Another character in the movie is the dog Spike, and he does not seem to like Tom at all. In the chasing scenes of the two main characters, they sometimes run to the garden - Spike's residence - and disturb his sleep. Most of the time, Tom would be the one who suffers Spike's anger while Jerry is having a big laugh. The plot is simple but the film Tom and Jerry always attracts a lot of audiences of all ages thanks to the lovely characters and funny circumstances. Although many years have gone by, the television channels have often displayed this film, and this is the indispensable spiritual food children.

Refer

Write about your favourite movie

Today I’d like to talk to you about Harry Porter which is one of my favourite films. It was a fiction film telling a story about people in the wizarding world. The central character was Harry Porter, who used to be an orphan in the normal world before discovering that he was a wizard. Afterwards, he went to a special school called Howard where taught him necessary skills to succeed in wizarding world. He also had to deal with challenges in terms of study, friendship, love and even the fight against dark power.
Harry Porter was recommended as a masterpiece that making me feel curious about it. Moreover, I had read the original novel before, and I really can’t put it down. So I guess the film would be as attractive as the book.
I think the most important reason why I enjoyed this film was that it made me feel adventurous. It was really a fantastic film.

Write about your favourite book

Favorite book and then the series "Doraemon" by Fujiko Fujio. The series told the cat from the future into the past Doremon same friends and help Nobita in the security context miracle. The main character is Doremon with your group Nobita, Shizuka, Xeko, Chaien. Extremely interesting story, engage the reader with the hilarious, witty, and full of magic. But it is also part of suspense through risky adventure of your group. The series is divided into two categories: short stories and novels. I enjoyed the long story, it's about the adventures in a strange land or through time times exciting but dangerous, and the group must go through many difficulties and from there we saw noble friendship bunch of kids. When I read the story I kept imagining myself as the character in that book that I could not put down. And I learned a lot from it especially friendships! If you have not read it try to read offline sure you will like it.

E tham khảo bài chị viết nhé

Surely everyone knows the movie the wizarding world Harry Potter, right? Of course, it is a movie that has been attached to the childhood of many people. One of my favorites is Harry Potter and the deathly hallows part 2. The film is adapted from the novel of the same name, Harry Potter by author J. K. Rowling. 

Harry Potter was released on July 15, 2011, since its release has won many prestigious awards such as Satellite Award, Saturn Award. Emma Watson, Richard Harris, and Rupert Grint are among the actors who became famous thanks to this movie.

The film tells the journey of the wizard boy Harry Potter and his two best friends, Ron Weasley and Hermione Granger, set at the Hogwarts School of Witchcraft and Wizardry. Movies about the old wizarding world were not known to many people, so when this movie explored the topic of witches, it became more popular. The highlight of the movie is that it was taken at a mystical school of magic, great effects, and a quality cast. 

I highly recommend this film to everybody - the storyline is amazing and the actors act their parts incredibly well - this is a MUST see! The reason I recommend everyone to watch this movie is that the actors here are very good. I think the crew is really lucky to have talented actors to play this movie. The trio of Harry, Hermione, and Ron have created their own brand for Harry Potter. The supporting characters like Snape, Malfoy, and Dumbledore are also great at acting. The film's effects are also a point to help a film become more popular. Do you remember the scene where Hermione and Ron were in the secret room was actually a green curtain behind them. In Goblet of Fire, the actor who plays Harry Potter (Daniel Radcliffe) has to dive into a deep lake to save people, and in real life, he also has to dive into the same lake without any help from the machine. 

The plot is really impressive, helping viewers feel like they are a character in the movie.Not only the movie, but the soundtrack of this movie also became more viral.The soundtrack helps listeners feel thrilling and attractive right from the first time listening. It also became a craze for a while and was made on many online forums.If you are someone who doesn't like watching movies about wizards, then you should watch Harry Potter, because it will change your mind.

Để 7a5b1 chia hết 3 thì 7+a+5+b+1 chia hết 3

                                 hay 13+a+b chia hết 3

Mà 0<a;b<9 => 13<a+b<31

Suy ra a+b=2;5;8;11;14;17

Mà a-b=4 nên a+b=b+4+b=2b+4 là số chẵn

Chỉ có a+b=2;8;14 thỏa mãn mà a;b là chữ số nên a+b>4

=>a+b=8;14

*Xét a+b=14

=>b=(14-4):2=5

<=>a=5+4=9

*Xét a+b=8

=>b=(8-4):2=2

<=>a=2+4=6

Vậy (a;b)=(6;2);(9;5)

để 7a5b1\(⋮3\)

\(\Rightarrow\)tổng các chữ số của nó \(⋮3\)

\(7+5+1=13\)

số \(⋮3\)là :15;18

ta có 2 trường hợp TH 1: 7+5+1+a+b=15

a+b=15-13=2

vì tổng của chúng =2 mà hiệu của chúng = 4

mà số a và b ko thể là số âm => ta loại TH này

TH 2: 7+5+1+a+b=18

a+b=18-(7+5+1)=5

a+b=5

a-b=4

ta áp dụng tính chất tìm 1 số khi bt tổng và hiệu của 2 số đó

ta có 2 TH 

TH 1: a là số lớn

a=(5+4):2=\(\frac{9}{5}\)ta loại TH này

TH2 a là số bé

(5-4):2=\(\frac{1}{2}\)ta loại TH này

tìm B:

TH1: b là số lớn :

(5+4):2=\(\frac{9}{5}\)ta loại TH này

TH2  b là số bé

(5+4):2=\(\frac{1}{2}\)ta loại TH này

vậy ta ko có số nào thỏa mãn ĐK của đề bài

Để : 7a5b1 \(⋮\)3

=> 7 + a + 5 + b + 1 \(⋮\)3

hay 13 + a + b\(⋮\)3

=> 13 + a + b = 15 hoặc 18 hoặc 21 hoặc 24 hoặc 27 hoặc 30

TH1 : 13 + a + b = 15

=> a + b = 2 

Mà a - b = 4 => Loại

Th2 : 13 + a + b = 18

=> a + b = 5

Mà a - b = 4 => a = 4,5 ; b = 0,5

=> Loại

TH3 :  13 + a + b = 21

=> a + b = 8

Mà a - b = 4

=> a = 6; b = 2   ( Thỏa mãn ) => Số 76521

TH4 : 13 + a + b = 24

=> a + b = 9

Mà a - b = 4

=> a = 6,5 ; b = 2,5 => Loại

Th5 : 13 + a + b = 27

=> a + b = 14

Mà a - b = 4

=> a = 9; b = 5   ( Thỏa mãn ) => Số 79551

TH6 : 13 + a + b = 30

=> a + b = 17

Mà a - b = 4

=> a = 10,5 ; b = 6,5 => Loại

Vậy có 2 trường hợp a,b thỏa mãn :

a = 6; b = 2 và a = 9; b = 5

Cs j sai thỳ ib ạ :3

Quê hương hai tiếng giản dị mà sao nghe thân thương kì lạ. Nhưng có rất nhiều cảnh đẹp như : cánh đồng lúa thẳng cánh cò bay chứa đựng bao nhiêu mồ hôi , những con sông như những dải lụa đào ,...thân thuộc nhất với em vẫn là cánh đồng lúa quê hương.

Quê hương tôi ngoài bãi đá bờ đê dòng sông bên lở bên bùi thì còn có cánh đồng lúa là thắng cảnh đẹp. Có thể nó không được thế giới cũng như nhà nước công nhận nhưng nó luôn là cảnh tượng đẹp nhất trong lòng tôi. Còn gì đẹp hơn khi nhìn thấy những cánh đồng lúa rộng thẳng cánh cò bay, một nét đẹp của cội nguồn dân tộc mà mỗi chúng ta nên tìm về để chiêm ngưỡng cũng như gìn giữ nó. Một nét đẹp giản dị mộc mạc mang màu xanh của hòa bình. 

Chúc bn học tốt ^^

em sinh ra và lớn lên trên quê hương thanh bình và yêu dấu.nơi đây có rất nhiều cảnh đẹp.đây là dòng sông quanh co uốn lượn tựa dải lụa mềm mại.kia là con đường làng in dấu đôi bàn chân bé nhỏ.kia nữa là đêm trăng sáng với những điệu hò du dương trầm bổng.nhưng có lẽ em yêu hơn cả là cảnh cánh đồng lúa vào một buổi sớm đẹp trời.

Vì a < 0 ; A > 0 và b < c

=>a và b là số nguyên âm .Còn c là số nguyên dương.

mà A > 0 nên c > 0 vì A=a.b.c

Vì b là số nguyên âm nên b < 0,do đó b.c <0

Vậy b < 0; c >0.

\(a+b+c=\dfrac{ab+ac}{2}=\dfrac{a\left(b+c\right)}{2}\Rightarrow\dfrac{b+c}{2}=\dfrac{a+b+c}{a}\)

\(\Rightarrow\dfrac{2}{b+c}=\dfrac{a}{a+b+c}\)

Tương tự ta có: \(\dfrac{3}{c+a}=\dfrac{b}{a+b+c}\)

\(\dfrac{4}{a+b}=\dfrac{c}{a+b+c}\)

Cộng vế với vế:

\(\dfrac{2}{b+c}+\dfrac{3}{c+a}+\dfrac{4}{a+b}=\dfrac{a}{a+b+c}+\dfrac{b}{a+b+c}+\dfrac{c}{a+b+c}=\dfrac{a+b+c}{a+b+c}=1\)

Vậy \(P=1\)