$\displaystyle n^2-1$ is divisible by 8 whenever n is an odd positive integer

1) Basic step: P(1) = 1-1 =0 is divisible by 8.

2) inductive step:

hypothesis:$\displaystyle P(k): k^2-1$ is divisible by 8

conclusion: $\displaystyle P(k+2): (k+2)^2 -1$ is divisible by 8?

OR

$\displaystyle P(k+1): (k+1)^2 -1$ is divisible by 8? <- to make it odd

help me pls