\(\frac{19}{13}+\frac{14}{6}+\frac{1}{9}+\frac{4}{6}+\frac{7}{13}+\frac{17}{9}\)

\(=\left(\frac{19}{13}+\frac{7}{13}\right)+\left(\frac{14}{6}+\frac{4}{6}\right)+\left(\frac{1}{9}+\frac{17}{9}\right)\)

\(=\frac{26}{13}+\frac{18}{6}+\frac{18}{9}\)

\(=2+3+2\)

\(=7\)

              \(\frac{315}{316}\times\frac{313}{314}\times\frac{316}{315}\times\frac{317}{314}\)

\(=\left(\frac{315}{316}\times\frac{316}{315}\right)\times\left(\frac{313}{314}\times\frac{317}{314}\right)\)

\(=1\times1,006339\)

\(=1,006339\)

#Chúc bạn học tốt !

#k mình nhé ?

Quy đồng tử, ta có:

\(\frac{3}{7}=\frac{15}{35}và\frac{5}{8}=\frac{15}{24}\)

Gọi phân số cần tìm là x

15/35 < x < 15/24

=> x = { 15/25; 15/26; 15/27; 15/28; 15/29; 15/30; 15/31; 15/32; 15/33; 15/34 }

1.Tan is very slow. He is late for school.

 Tom is so …………………......................................................................…………………………..

2.The man speaks loudly. He wants every one to hear him clearly.

The man speaks loudly so that ……............……………......................................…………………..

3.This exercise is easier than that one.

That exercise is not ………………….........................................................…………………………..

4.We wrote this letter for two hours.

It took …………………..............................................................................…………………………..

5.I spend a day painting this house.

It takes………………….............................................................................…………………………..

6.Dogs are difficult to train.

7.They think that learning English are not easy.

 They think that it …………………............................................…………………………..

8.The weather is too cold for us to go out.

The weather is so ………….......................................................................…………………………..

9.The weather is too cold for us to go out.

àThe weather isn’t…………………..............................................................…………………………..

10.     The film isn’t interesting for us to see.

The film is too…………………....................................................................…………………………..

11.     Nhan is tired. He can’t fly his kites.

→ Nhan is so …………………......................................................................…………………………..

12. I wish to have enough money. I want to buy a new house

→ I wish to have enough money so that…….................................................…………………………..

13. I don’t think this book is expensive as it is.

→ This book is.....................................................................................................................................

14. Doing this test is very difficult.

→ It’s....................................................................................................................................................

15. He said something. I didn’t understand.

→ I didn’t understand...........................................................................................................................

16. He s to read very much.

→ He enjoys.........................................................................................................................................

17. The bag is very heavy.  I can’t carry it.

→ This bag is too ................................................................................................................................

18. We’ll go out. The rain will stop

→ When..............................................................................................................................................

a, n + 4  ⋮ n

Ta có : n  ⋮ n

=> Để n + 4  ⋮ thì 4 phải chia hết chọn :

Mà n ∈ N => n ∈ { 1 ; 2 ; 4 }

Vậy với n ∈ { 1 ; 2 ; 4 } thì  n + 4  ⋮ n .

b, 3n + 7 ⋮ n

Để  3n + 7 ⋮ n thì :

 7 ⋮ n ( vì 3n ⋮ n ) mà n ∈ N

n ∈ { 1 ; 7 }

Vậy với n ∈ { 1 ; 7} thì  3n + 7 ⋮ n .

c, 27 - 5n ⋮ n

Để 27 - 5n ⋮ n thì :

27 ⋮ n ( vì 5n ⋮ n ) mà n  ∈ N . 

n  ∈ { 1 ; 3 ; 9 ; 27 }

Vậy với n  ∈ { 1 ; 3 ; 9 ; 27 } thì 27 - 5n ⋮ n .

a.

Đặt \(\left\{{}\begin{matrix}\sqrt{x^2+2x+3}=a>0\\\sqrt{x^2+x+2}=b>0\end{matrix}\right.\) \(\Rightarrow a^2-b^2=x+1\)

Pt trở thành:

\(a+b=2\left(a^2-b^2\right)\)

\(\Leftrightarrow a+b=\left(2a-2b\right)\left(a+b\right)\)

\(\Leftrightarrow2a-2b=1\) (do \(a+b>0\))

\(\Leftrightarrow2a=2b+1\)

\(\Leftrightarrow2\sqrt{x^2+2x+3}=2\sqrt{x^2+x+2}+1\)

\(\Leftrightarrow4\left(x^2+2x+3\right)=4\left(x^2+x+2\right)+1+4\sqrt{x^2+x+2}\)

\(\Leftrightarrow4x+3=4\sqrt{x^2+x+2}\)

\(\Leftrightarrow\left\{{}\begin{matrix}x\ge-\dfrac{3}{4}\\16\left(x^2+x+2\right)=\left(4x+3\right)^2\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x\ge-\dfrac{3}{4}\\8x=23\end{matrix}\right.\) \(\Rightarrow x=\dfrac{23}{8}\)

b.

ĐKXĐ: \(x\ge3\)

Đặt \(\left\{{}\begin{matrix}\sqrt{x-3}=a\ge0\\\sqrt{x+2}=b>0\end{matrix}\right.\) \(\Rightarrow a^2-b^2=-5\)

Phương trình trở thành:

\(\left(a-b\right)\left(ab+1\right)=a^2-b^2\)

\(\Leftrightarrow\left(a-b\right)\left(ab+1\right)=\left(a-b\right)\left(a+b\right)\)

\(\Leftrightarrow\left[{}\begin{matrix}a=b\left(vô-nghiệm\right)\\ab+1=a+b\end{matrix}\right.\)

\(\Rightarrow ab-a-b+1=0\)

\(\Leftrightarrow\left(a-1\right)\left(b-1\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}a=1\\b=1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}\sqrt{x-3}=1\\\sqrt{x+2}=1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=4\\x=-1\left(ktm\right)\end{matrix}\right.\)

Diện tích hình chữ nhật là :

34,5 x 12,7 = 438,15 ( m2 )

Chu vi hình chữ nhật là :

( 34,5 + 12,7 ) x 2 = 94,4 ( m )

Đáp số : Diện tích : 438,15 m2 .

             Chu vi : 94,4 m .

Chào mừng bạn đến căn nhà tri thức Online Math ! Mk sẽ luôn giúp đỡ bạn !

Chu vi hình chữ nhật là :

( 34,5 + 12,7 ) x 2 = 94,4 ( m )

Diện tích hình chữ nhật là :
34,5 x 12,7 = 438,15 ( m² )

      Đáp số : .......
 

diện tích là

         34,5x12,7=438,15(\(m^2\))

chu vi là

     (34,5+12,7)x2=94,4(m)

\(\frac{x+1}{3}=\frac{9}{2}\)

\(\left(x+1\right).2=9.3\)

\(\left(x+1\right).2=27\)

\(x+1=27:2\)

\(x+1=13,5\)

\(x=13,5-1=12,5\)

vậy x = 12.5

\(\frac{x+1}{3}=\frac{9}{2}\)

\(\Leftrightarrow2\left(x+1\right)=3\times9\)

\(\Leftrightarrow2\left(x+1\right)=27\)

\(\Leftrightarrow x+1=\frac{27}{2}\)

\(\Leftrightarrow x=\frac{25}{2}\)

\(\frac{x+1}{3}\)= \(\frac{9}{2}\)

:> 2( x +1) = 9 . 3

:> 2x + 2 = 27

:>       2x = 27 - 2

:>       2x = 25

:>        x = \(\frac{25}{2}\)

Các bn giúp mk với

gọi d là (4n+7,3n+2)

ta có : 

4n+7 chia hết cho d

3n+2 chia hết cho d

=>3(4n+7)-4(3n+2)=12n+21-12n-8=13

=>d=13=>hai số trên là 2 số nguyên tố cùng nhau( chắc sai hihi)

Gọi ƯCLN(4n+7,3n+2)=d

=>\(\hept{\begin{cases}4n+7⋮d\\3n+2⋮d\end{cases}}\)=>\(\hept{\begin{cases}3\left(4n+7\right)⋮d\\4\left(3n+2\right)⋮d\end{cases}}\)=>\(\hept{\begin{cases}12n+21⋮d\\12n+8⋮d\end{cases}}\)

<=> 12n + 21 - 12n -8 \(⋮\)d

<=> 21 - 8 \(⋮\)d

<=> 13  \(⋮\)d

<=> d \(\in\)Ư(13)

<=> d \(\in\){1;13}

Vậy 4n + 7 và 3n + 2 có thể là 2 số nguyên tố cùng nhau hoặc ko phải 2 số nguyên tố cùng nhau

(chắc sai rồi):| đúng nhớ K