Unit digit of $4:$

- $4^{1} = 4$
- $4^{2} = 16$

We can say that unit digit of $4$ is $4^{\text{odd}} = 4$ and $4^{\text{even}} = 6$

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Unit digit of $9:$

- $9^{1} = 9$
- $9^{2} = 81$

We can say that unit digit of $9$ is $9^{\text{odd}} = 9$ and $9^{\text{even}} = 1$