Tìm x thuộc Z , biết: a, 25 chia hết ( x + 2 ) b, ( 2x + 4 ) chia hết x c, ( x + 7 ) chia hết ( x + 3 ) d, ( 3x - 5 ) chia hết ( x - 1 )

@MinhAnh

`a)`

`25 \vdots x + 2`

`=> x + 2 \in Ư_((25))`

Ta có bảng:

$$\begin{array}{|c|c|c|}\hline \text{x+2}&\text{-1}&\text{-25}&\text{-5}&\text{5}\\\hline \text{x}&\text{-3}&\text{-27}&\text{-7}&\text{3}\\\hline\end{array}$$

`b)`

`2x + 4 \vdots x`

`=>{(2x+4 \vdots x),( 2(x) \vdots x ):}`

`=>{(2x+4 \vdots x),( 2x \vdots x):}`

`=> (2x+4)-2x \vdots x`

`=> 2x + 4 - 2x \vdots x`

`=> 4 \vdots x`

`=> x \in Ư_((4))`

$$\begin{array}{|c|c|c|}\hline \text{x}&\text{-2}&\text{2}&\text{-1}&\text{1}&\text{-4}&\text{4}\\\hline\end{array}$$

`c)`

`x + 7 \vdots x + 3`

`=> (x+7)-(x+3) \vdots x+3`

`=> x + 7 - x - 3 \vdots x + 3`

`=> 4 \vdots x + 3`

`=> x+3 \in Ư_((4))`

Ta có bảng: $$\begin{array}{|c|c|c|}\hline \text{x+3}&\text{-2}&\text{2}&\text{-4}&\text{4}&\text{-1}&\text{1}\\\hline \text{x}&\text{-5}&\text{-1}&\text{-7}&\text{1}&\text{-4}&\text{-2}\\\hline\end{array}$$

`d)`

`3x - 5 \vdots x - 1`

`=>{(3x-5 \vdots x - 1),( 3(x-1) \vdots x-1):}`

`=>{(3x-5 \vdots x - 1),( 3x-3 \vdots x -1):}`

`=>(3x-5)-(3x-3) \vdots x - 1`

`=>3x - 5 - 3x + 3 \vdots x - 1`

`=>-2 \vdots x - 1`

`=> x - 1 \in Ư_((-2))`

Ta có bảng:

$$\begin{array}{|c|c|c|}\hline \text{x-1}&\text{-1}&\text{1}&\text{-2}&\text{2}\\\hline \text{x}&\text{0}&\text{2}&\text{-1}&\text{3}\\\hline\end{array}$$