Question

Bài 1 : Tìm x biết :

\(\frac{x}{3}=-\frac{12}{9}\)

\(\frac{4}{5}x-\frac{8}{5}=-\frac{1}{2}\)

\(\frac{1}{5}.\left|x\right|-1\frac{2}{5}=\frac{2}{5}\)

Bài 2 : Tìm tất cả các số nguyên để \(\frac{n+1}{n-2}\) là số nguyên.

Ai nhanh mk tick

Answer 1

x/3 = -12/9

=> x/3 = -4/3

=> x = -4

vậy_

Answer 2

1.Ta có: \(\frac{x}{3}=-\frac{12}{9}\)

=> \(\frac{3x}{9}=-\frac{12}{9}\)

=> 3x = -12

=> x = -12 : 3

=> x = -4

\(\frac{4}{5}x-\frac{8}{5}=-\frac{1}{2}\)

=> \(\frac{4}{5}x=-\frac{1}{2}+\frac{8}{5}\)

=> \(\frac{4}{5}x=\frac{11}{10}\)

=> \(x=\frac{11}{10}:\frac{4}{5}\)

=> \(x=\frac{11}{8}\)

Answer 3

bài 1: \(\frac{x}{3}=\frac{-12}{9}\)=> 9x=-36

=> x=-4

vậy x=-4

\(\frac{4}{5}x-\frac{8}{5}=\frac{-1}{2}\)=> \(\frac{4}{5}x=\frac{-1}{2}+\frac{8}{5}\)

=> \(\frac{4}{5}x=\frac{-5}{10}+\frac{16}{10}\)=\(\frac{11}{10}\)=> \(x=\frac{11}{10}:\frac{4}{5}\)=\(\frac{11}{10}.\frac{5}{4}\)=\(\frac{11}{8}\)

vậy x=\(\frac{11}{8}\)

\(\frac{1}{5}.\left|x\right|-1\frac{2}{5}=\frac{2}{5}\)=> \(\frac{1}{5}.\left|x\right|-\frac{7}{5}=\frac{2}{5}\)

=> \(\frac{1}{5}.\left|x\right|=\frac{2}{5}+\frac{7}{5}=\frac{9}{5}\)=> |x| =\(\frac{9}{5}:\frac{1}{5}\)=9

=> x=9 hoặc x=-9

vậy x=9 hoặc x=-9

Answer 4

1.\(\frac{1}{5}\left|x\right|-1\frac{2}{5}=\frac{2}{5}\)

=> \(\frac{1}{5}\left|x\right|=\frac{2}{5}+\frac{7}{5}\)

=> \(\frac{1}{5}\left|x\right|=\frac{9}{5}\)

=> \(\left|x\right|=\frac{9}{5}:\frac{1}{5}\)

=> \(\left|x\right|=9\)

=> \(\orbr{\begin{cases}x=9\\x=-9\end{cases}}\)

Bài 2: Ta có: \(\frac{n+1}{n-2}=\frac{\left(n-2\right)+3}{n-2}=1+\frac{3}{n-2}\)

Để \(\frac{n+1}{n-2}\)là số nguyên <=> 3 \(⋮\)n - 2

<=> n - 1 \(\in\)Ư(3) = {1; -1; 3; -3}

Lập bảng :

n - 1	1	-1	3	-3
n	2	0	4	-2

Vậy ...

Answer 5

Bài 1 :

\(\frac{x}{3}=\frac{-12}{9}\)

\(\Rightarrow\frac{3x}{9}=\frac{-12}{9}\)

\(\Rightarrow3x=-12\)

\(\Rightarrow x=-4\)

Answer 6

\(\frac{4}{5}x-\frac{8}{5}=-\frac{1}{2}\)

\(\Rightarrow\frac{4}{5}x=-\frac{1}{2}+\frac{8}{5}\)

\(\frac{4}{5}x=\frac{11}{10}\)

\(\Rightarrow x=\frac{11}{10}:\frac{4}{5}\)

\(x=\frac{11}{8}\)

Answer 7

\(\frac{1}{5}.|x|-1\frac{2}{5}=\frac{2}{5}\)

\(\Rightarrow\frac{1}{5}.|x|=\frac{2}{5}+\frac{7}{5}\)

\(\frac{1}{5}.|x|=\frac{9}{5}\)

\(\Rightarrow|x|=\frac{9}{5}:\frac{1}{5}=9\)

\(\Rightarrow\hept{\begin{cases}x=9\\x=-9\end{cases}}\)

Answer 8

kudo shinichi n - 2 chứ k phải n - 1 nhá =))

2.

Để \(\frac{n+1}{n-2}\in Z\) thì \(n\in Z\)

\(\frac{n+1}{n-2}=\frac{n-2+3}{n-2}=1+\frac{3}{n-2}\)

Để \(\frac{n+1}{n-2}\in Z\)thì \(\frac{3}{n-2}\in Z\)

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

\(\Rightarrow n\in\left\{-1;1;3;5\right\}\)