Sunday 31 July 2016

elementary number theory - Prove that $4^n+ 1$ is not divisible by $3$

For all integers $n \ge 0$, prove that the value $4^n + 1$ is not divisible by 3.



I need to use Proof by Induction to solve this problem. The base case is obviously 0, so I solved $4^0 + 1 = 2$. 2 is not divisible by 3.



I just need help proving the inductive step. I was trying to use proof by contradiction by saying that $4^n + 1 = 4m - 1$ for some integer $m$ and then disproving it. But I'd rather use proof by induction to solve this question. Thanks so much.

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