Question

Tìm số nguyên n, sao cho: 2n - 5 chia hết cho n + 7.

Answer 1

\(\Leftrightarrow n+7\in\left\{1;-1;19;-19\right\}\)

hay \(n\in\left\{-6;-8;12;-26\right\}\)

Answer 2

\(\Rightarrow2\left(n+7\right)-19⋮n+7\\ \Rightarrow n+7\inƯ\left(19\right)=\left\{-19;-1;1;19\right\}\\ \Rightarrow n\in\left\{-26;-8;-6;12\right\}\)