Ta có: 12 \(⋮\)x-1
\(\Rightarrow\) x - 1 \(\in\) Ư(12) = {1; 2; 3; 4; 6; 12}
\(\Rightarrow\) x \(\in\) {2; 3; 4; 5; 7; 13}
Vậy: x \(\in\) {2; 3; 4; 5; 7; 13}
\(12⋮\left(x-1\right)\)
\(\Leftrightarrow\left(x-1\right)\inƯ\left(12\right)=\left\{1;2;3;4;6;12\right\}\)
Ta có bảng sau
| x-1 | 1 | 2 | 3 | 4 | 6 | 12 |
| x | 2 | 3 | 4 | 5 | 7 | 13 |