Proof by induction consists in following scheme:
or intuitively, let be a predicate $ P(n) $ with $ n \in \Bbb{N} $:
if
- $P(0) $ is true
- $P(k)\to P(k+1), \forall k \in \Bbb{N} $ is true
then $P(n), \forall n \in \Bbb{N}$ is true
but can I proof by contradiction the point 2?