Question

Tìm n € Z bt

a, 2n + 3 chia hết cho n + 4

b, n^2 + 3n chia hết cho n + 4

c, n^2 + 3 chia hết cho n - 2

Answer 1

a: \(\Leftrightarrow2n+8-5⋮n+4\)

\(\Leftrightarrow n+4\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{-3;-5;1;-9\right\}\)

b: \(\Leftrightarrow n^2+4n-n-4+4⋮n+4\)

\(\Leftrightarrow n+4\in\left\{1;-1;2;-2;4;-4\right\}\)

hay \(n\in\left\{-3;-5;-2;-6;0;-8\right\}\)

c: \(\Leftrightarrow n^2-4+7⋮n-2\)

\(\Leftrightarrow n-2\in\left\{1;-1;7;-7\right\}\)

hay \(n\in\left\{3;1;9;-5\right\}\)