Ta có:
1000 chia hết cho 8 => 10^3 chia hết cho 8
=>10^25.10^3 chia hết cho 8
và 8 chia hết cho 8
=>10^28+8 chia hết cho 8 (1)
Lại có 10^28+8= 1000....08(27 CS 0)
=>10^28+8 chia hết cho 9 (2)
Lại vì ƯCLN (8;9)=1 (3)
Từ (1);(2);(3)=>10^28+8 chia hết cho 72
k mk nha

:3

thank b

giai cho mink voi

a, DK:x khac -5

de A co gia tri nguyen thi (3x-1)/(x+5) co gia tri nguyen. Phan h ta duoc:3 - (16)/(x+5).

De 3 - (16)/(x+5) co gia tri nguyen thi (x+5) thuoc uoc cua 16

nen x=(-1;-9;11;-21;-4;-6)

a) -3/7 + 5/13 + -4/7 

= ( -3/7 + -4/7 ) + 5/13

= -7/7 +5/13

= -1 + 5/13

= -13/13 + 5/13

= -8/13

b) -5/21 + -2/21 + 8/24

= -7/21 + 8/24

= -1/3 + 1/3 

= 0

a) \(\frac{-3}{7}+\frac{5}{13}+\frac{-4}{7}\)

\(=\left(\frac{-3}{7}+\frac{-4}{7}\right)+\frac{5}{13}\)

\(=\left(-1\right)+\frac{5}{13}\)

\(=-1\frac{5}{13}\)

b) \(\frac{-5}{21}+\frac{-2}{21}+\frac{8}{24}\)

\(=\left(\frac{-5}{21}+\frac{-2}{21}\right)+\frac{1}{3}\)

\(=\frac{-1}{3}+\frac{1}{3}\)

\(=0\)

Từng bài 1 thôi nha bn!!!

a) Xét hiệu: A = 9.(7x+4y) - 2. (13x+18y)

A = 63x + 36y - 26x - 36y

A = 37x \(\Rightarrow A⋮37\) Vì 7x + 4y chia hết cho 37

9.(7x+4y) chia hết cho 37

Mà A chia hết cho 37 

\(2\left(13x+18y\right)⋮37\)

Do 2 và 37 là nguyên tố cùng nhau

13x+18y chia hết cho 37

Vậy nếu 7x+4y chia hết cho 37 thì 13x+18y chia hết cho 37 

VP đâu bạn?

\(x=\frac{5684}{837}nha\)

62/7*x=1624/27

x=1624/27chia 62/7

x=5684/837

k nha

\(n+5⋮n-3\)

\(\Rightarrow n-3+8⋮n-3\)

     \(n-3⋮n-3\)

\(\Rightarrow8⋮n-3\)

\(\Rightarrow n-3\inƯ\left(8\right)\)

     \(n\inℤ\Rightarrow n-3\inℤ\)

\(\Rightarrow n-3\in\left\{-1;1;-2;2;-4;4-8;8\right\}\)

\(\Rightarrow n\in\left\{2;4;1;5;-1;7;-5;11\right\}\)

\(n+5⋮n-3\)

\(\Leftrightarrow\left(n-3\right)+8⋮n-3\)

-Mà: \(n-3⋮n-3\Rightarrow8⋮n-3\)

\(\Leftrightarrow n-3\inƯ\left(8\right)\)

\(\Rightarrow.....\)

Áp dụng BĐT \(\frac{a}{b}+\frac{b}{c}+\frac{c}{d}>\frac{a+b+c}{a+b+c}=1>\frac{a+b+c}{b+c+d}\).

\(\Rightarrow\frac{2010}{2011}+\frac{2011}{2012}+\frac{2012}{2013}>\frac{2010+2011+2012}{2010+2011+2012}>\frac{2010+2011+2012}{2011+2012+2013}\)mà 2010 + 2011 + 2012 < 2011+2012+2013 ,suy ra \(\frac{2010+2011+2012}{2011+2012+2013}< 1\))

\(\Rightarrow\frac{2010}{2011}+\frac{2011}{2012}+\frac{2012}{2013}>\frac{2010+2011+2012}{2011+2012+2013}\)hay P > Q 

Vậy P > Q

b) Áp dụng công thức BCNN (a, b) . UCLN (a,b) = a.b

\(\Rightarrow a.b=420.21=8820\)

Ta có:

\(ab=8820\)

\(a+21=b\Rightarrow b-a=21\)

Hai số cách nhau 21 mà có tích là 8820 là 84 , 105

Mà a + 21 = b suy ra a < b

Vậy a = 84 ; b = 105

a,-Cách khác:

-Ta có: \(\frac{2010+2011+2012}{2011+2012+2013}=\frac{2010}{2011+2012+2013}+\frac{2011}{2011+2012+2013}+\frac{2012}{2011+2012+2013}\)

-Mà: \(\frac{2010}{2011}>\frac{2010}{2011+2012+2013}\left(1\right)\)

\(\frac{2011}{2012}>\frac{2011}{2011+2012+2013}\left(2\right)\)

\(\frac{2012}{2013}>\frac{2012}{2011+2012+2013}\left(3\right)\)

\(\Rightarrow P>Q\)

= 1/3+5/7=22/21 k mik nha

sau đó kb vs mik nha

\(\frac{1}{3}+|-\frac{5}{7}|\)

\(=\frac{1}{3}+\frac{5}{7}\)

\(=\frac{7}{21}+\frac{15}{21}\)

\(=\frac{22}{21}\)