Question

tìm stn N cho biết 2n + 7 chia hết cho n+1

Answer 1

\(2n+7⋮n+1\)

\(\Leftrightarrow5⋮n+1\)

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

hay \(n\in\left\{0;4\right\}\)

Answer 2

 

2n+7⋮n+12n+7⋮2n+1

⇒(2n+1)+6⋮n+1⇒(2n+1)+6⋮2n+1

⇒6⋮2n+1⇒6⋮2n+1(vì 2n+1⋮
n+12n+1⋮2n+1)

⇒n+1∈Ư(6)⇒2n+1∈Ư(6)

$\Rightarrow \mathrm{n}+1\in \left\{1;2;3;6\right\}$

$\Rightarrow$$\mathrm{n}\in \left\{0;1;2;5\right\}$