Tìm số nguyên x,biết : x + 2 chia hết cho x x - 5 chia hết cho x + 2 3x + 5 chia hết cho x - 2 (Cấm chép timi)

a/ $\displaystyle x+2\vdots x$
vì $\displaystyle x\vdots x\Rightarrow 2\vdots x$
Mà $\displaystyle x\in \mathbb{Z} \Rightarrow x\in Ư( 2) =\{\pm 1;\pm 2\}$
Vậy $\displaystyle x\in \{-2;-1;1;2\}$
b/ 
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
( x-5) \vdots ( x+2)\\
\Rightarrow ( x+2) -7\vdots ( x+2)
\end{array}$
Vì $\displaystyle ( x+2) \vdots ( x+2) \Rightarrow -7\vdots ( x+2)$
Mà $\displaystyle x\ \in \mathbb{Z} \Rightarrow ( x+2) \in Ư( -7) =\{-1;1;-7;7\}$.
$\displaystyle \Rightarrow x\in \{-3;\ -1;\ -9;\ 5\}$ 

c/
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
( 3x+5) \vdots ( x-2)\\
\Rightarrow 3( x-2) +11\vdots ( x-2)
\end{array}$
Vì $\displaystyle ( x-2) \vdots ( x-2) \Rightarrow 3( x-2) \vdots ( x-2) \Rightarrow 11\vdots ( x-2)$
Mà $\displaystyle x\in \mathbb{Z} \Rightarrow ( x-2) \in Ư( 11) =\{-1;1;11;-11\}$.
$\displaystyle \Rightarrow x\in \{1;3;13;-9\}$