\(S\left(n\right)=n^2-2015n+8\)
- Nếu \(n< 2015\Rightarrow S\left(n\right)=n^2-2015n+8< n^2-2015n+2014\)
\(\Rightarrow S\left(n\right)< \left(n-1\right)\left(n-2014\right)\le0\) (vô lý)
- Nếu \(n>2015\Rightarrow n-2015\ge1\)
\(\Rightarrow S\left(n\right)=n\left(n-1015\right)+8\ge n+8\) (vô lý)
- Nếu \(n=2015\Rightarrow S\left(n\right)=8\) (thỏa mãn)
Vậy \(n=2015\)