[tex] \frac{3}{x + 1} \: \in \: \mathbb{N} = > x + 1 \: \: \vdots \: \: 3[/tex]
[tex]=>x+1\:\in\:D_{3}[/tex]
[tex] = > x + 1 \: \in \: \left \{ \pm1,\pm3 \right \}[/tex]
[tex]x + 1 = - 1 = > x = - 2 \: \notin \: \mathbb{N}[/tex]
[tex]x + 1 = 1 = > x = 0 \: \in \: \mathbb{N}[/tex]
[tex]x + 1 = - 3 = > x = - 4 \: \notin \: \mathbb{N}[/tex]
[tex]x + 1 = 3 = > x = 2 \: \in \: \mathbb{N}[/tex]
[tex]S=\left \{ 0,2 \right \}[/tex]
[tex]=>B)\left \{ 0,2 \right \}[/tex]
