Toán Lớp 6: (3n + 1) chia hết cho (n + 2).
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Toán Lớp 6: (3n + 1) chia hết cho (n + 2).
Comments ( 1 )
3n + 1\\
= 3n + 6 – 5\\
= 3.\left( {n + 2} \right) – 5\\
Do:3\left( {n + 2} \right) \vdots \left( {n + 2} \right)\\
\Leftrightarrow 5 \vdots \left( {n + 2} \right)\\
\Leftrightarrow \left( {n + 2} \right) \in \left\{ { – 5; – 1;1;5} \right\}\\
\Leftrightarrow n \in \left\{ { – 7; – 3; – 1;3} \right\}\\
Vậy\,n \in \left\{ { – 7; – 3; – 1;3} \right\}
\end{array}$