Question

Tìm nϵN để : 

\(n^2+3n+5:n+1\)

Answer 1

\(\Leftrightarrow n^2+n+2n+2+3⋮n+1\)

\(\Leftrightarrow n+1\in\left\{1;3\right\}\)

hay \(n\in\left\{0;2\right\}\)

Answer 2

$(n^2+3n+5)\vdots (n+1)$

$\to (n^2+n+2n+2+3)\vdots (n+1)$

$\to [n(n+1)+2(n+1)+3]\vdots (n+1)$

$\to n+1\in Ư(3)=\left\{-3;-1;1;3\right\}$

$\to n\in \left\{-4;-2;0;2\right\}$

Mà $n\in \mathbb{N}$

$\to n\in \left\{0;2\right\}$

Answer 3

0,2