Question

[Vũ Lâm Tùng]

Tìm số nguyên n để 2n+7 chia hết cho 3n-1

Answer 1

[Nguyễn Hoàng Minh]

\(\Rightarrow6n-14⋮3n-1\\ \Rightarrow2\left(3n-1\right)-12⋮3n-1\\ \Rightarrow3n-1\inƯ\left(12\right)=\left\{-12;-6;-4;-3;-2;-1;1;2;3;4;6;12\right\}\\ \Rightarrow3n\in\left\{-3;0;3\right\}\left(n\in Z\right)\\ \Rightarrow n\in\left\{-1;0;1\right\}\)

Answer 2

[Nguyễn Lê Phước Thịnh]

\(\Leftrightarrow3n-1\in\left\{1;-1;2;-2;4;-4;8;-8;16;-16\right\}\)

hay \(n\in\left\{0;1;-1;3;-5\right\}\)