Proof with Binomial Theorem

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Quick question! if I have $\varphi= (1 +\sqrt{5})/2$ and $\psi = (1 - \sqrt{5})/2$ and $n\ge0$ would be an int

How would I prove that in $(\varphi^n - \psi^n)/\sqrt{5}$ is an integer but only using Newtons binomial theorem?