show $\alpha=t^{1/p}$ is not separable over $F.$

Question

I had this question in my exam ,but don't know how to proceed:

Let $F=\mathbb Z/p\mathbb Z(t)$ where $t$ is indeterminate. Then show $\alpha=t^{1/p}$ is not separable over $F.$

What I know is that an element is called separable over $F$ if it is algebraic over $F$ and its minimal polynomial over $F$ is a separable polynomial.

Kindly help how to start with ...