ISI2015-DCG-13

Question

For all the natural number $n \geq 3, \: n^2+1$ is

• A. divisible by $3$
• B. not divisible by $3$
• C. divisible by $9$
• D. None of these

Answer 1

if we take $n=4$ then $n^2+1=17$ which is not divisible by $3$ and $9$.

So option a and c are eliminated.

Option B. is correct option.

For proof refer this