Question

2n+7 chia het cho n-2

n^2+3n +4 chia hey cho n+3

tim so tu nhien n

 

Answer 1

\(\frac{2n+7}{n-2}=\frac{2n-4+11}{n-2}=\frac{2.\left(n-2\right)}{n-2}+\frac{11}{n-2}=2+\frac{11}{n-2}\)

Mà \(2\in N\Rightarrow n-2\inƯ\left(11\right)\)

\(\Rightarrow n-2=\left\{1;11\right\}\)

\(\Rightarrow n\in\left\{3;13\right\}\)

\(\frac{n^2+3+4}{n+3}=\frac{n.n+3n+4}{n+3}=\frac{n.\left(n+3\right)}{n+3}+\frac{4}{n+3}=n+\frac{4}{n+3}\)

Mà \(n\in N\Rightarrow n+3\inƯ\left(4\right)\Rightarrow n+3\in\left\{1;4\right\}\Rightarrow n\in\left\{-2;1\right\}\)

Mà n là số tự nhiên => n = 1