\(2x+7\,\,\,\vdots\,\,\,2x-1\)
\(\Leftrightarrow 2x-1+1+7\,\,\,\vdots\,\,\,2x-1\)
\(\Leftrightarrow (2x-1)+8\,\,\,\vdots\,\,\,2x-1\)
\(\Leftrightarrow 8\,\,\,\vdots\,\,\,2x-1\)
\(\Leftrightarrow 2x-1\,\,\,\in\,\,\,Ư(8)=\)`{\pm 1;\pm 2;\pm 4;\pm 8}`
\(\Leftrightarrow 2x\,\,\,\in\,\,\,\)`{2;0;3;-1;5;-3;9;-7}`
\(\Leftrightarrow x\,\,\,\in\,\,\,\)`{1;0;3/2;-1/2;5/2;-3/2;9/2;-7/2}`
Nếu \(x\,\,\,\in\mathbb\,\,\,{Z}\)
\(\Rightarrow x\,\,\,\in\,\,\,\)`{\pm 1}`
