11⋮ (x - 1) ⇒ (x - 1 ) ∈ Ư ( 11)
(x - 1 ) ∈ Ư ( 11) = { 1; 11}
⇒ x ∈ { 2;12}
\(11⋮\left(x-1\right)\)
\(\Rightarrow x-1\inƯ\left(11\right)\)
\(\Rightarrow x-1\in\left\{1;11;-1;-11\right\}\)
\(\Rightarrow x\in\left\{2;12;0;-10\right\}\)