Question

Tìm số nguyên n biết : 3n+7 chia hết cho 2n + 3

Answer 1

Lời giải:

$3n+7\vdots 2n+3$

$\Rightarrow 2(3n+7)\vdots 2n+3$

$\Rightarrow 6n+14\vdots 2n+3$

$\Rightarrow 3(2n+3)+5\vdots 2n+3$

$\Rightarrow 5\vdots 2n+3$
$\Rightarrow 2n+3\in \left\{1; -1; 5; -5\right\}$

$\Rightarrow n\in \left\{-1; -2; 1; -4\right\}$