## Statement

Every odd number can be written as a multiple of two plus one.

$$ 2k + 1, \text{where} \space k \in \Z $$

## Proof

These are the even numbers:

$$ ..., -3, -1, 1, 3, 5, 7, 9 $$

Note that every odd number is two more than the previous one.

So every even number can be written as two times a whole number $ k $ plus one.

$$ 2 * k + 1, \text{where} \space k \in \Z $$