Question

Tìm n ∈ N

 n² + 7n + 9 chia hết cho n + 7

Answer 1

\(\Rightarrow n\left(n+7\right)+9⋮n+7\\ \Rightarrow n+7\inƯ\left(9\right)=\left\{1;3;9\right\}\\ \Rightarrow n=2\left(n\in N\right)\)

Answer 2

\(\Leftrightarrow n+7=9\)

hay n=2