\(3n+1⋮n-1\)
\(\Rightarrow3.\left(n-1\right)+4⋮n-1\)
Vì \(3.\left(n-1\right)⋮n-1\)=> \(4⋮n-1\)
Hay \(n-1\inƯ\left(4\right)=\left\{1;2;4\right\}\)
Ta có bảng sau :
n-1 | 1 | 2 | 4 |
n | 2 | 3 | 5 |
Vậy ....
cac ban lam tung buoc cho minh nhe..huhu
3n+1chia het cho n-1
-->3n-3+4 chia het cho n-1
-->4 chia het cho n-1
--> n-1 thuoc 2;1;4
-->n thuoc 2;3;5