Đáp án:
b) \(\left[ \begin{array}{l}
n = 16\\
n = 6
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a)6n + 9 \vdots 3n + 2\\
\to 2\left( {3n + 2} \right) + 5 \vdots 3n + 2\\
\to 5 \vdots 3n + 2\\
\Leftrightarrow 3n + 2 \in U\left( 5 \right)\\
\to \left[ \begin{array}{l}
3n + 2 = 5\\
3n + 2 = 1
\end{array} \right.\\
\to \left[ \begin{array}{l}
n = 1\\
n = - \dfrac{1}{3}\left( l \right)
\end{array} \right.\\
b)2n + 1 \vdots n - 5\\
\to 2\left( {n - 5} \right) + 11 \vdots n - 5\\
\to 11 \vdots n - 5\\
\to n - 5 \in U\left( {11} \right)\\
\to \left[ \begin{array}{l}
n - 5 = 11\\
n - 5 = 1
\end{array} \right.\\
\to \left[ \begin{array}{l}
n = 16\\
n = 6
\end{array} \right.
\end{array}\)
