Question

 Cho A = 8 : ( n - 2 ) 

Tìm n ϵ N để A ϵ N 

Answer 1

Để A là số tự nhiên thì \(\left\{{}\begin{matrix}8⋮n-2\\n>2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}n-2\in\left\{1;-1;2;-2;4;-4;8;-8\right\}\\n>2\end{matrix}\right.\)

hay \(n\in\left\{3;4;6;10\right\}\)

Answer 2

`=> n - 2 in Ư(8)`

Ta có: `n in NN => n - 2 >= -2`.

`-> n - 2 in {-1, -2, 1, 2, 4, 8}`

`=> n - 2 in {1, 0, 3, 4, 6, 10}`.