How do I add the elements of a finite field knowing the multiplicative structure?

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Let $F$ be a finite field then the multiplicative part $F^\times$ is a cyclic group generated by $f$.

What - when nonzero - is $f^i + f^j$ as a power of $f$? What is 1,2,3,4,.. in terms of $f$?


For example $\mathbb F_{2^2} = \mathbb F_2[X]/(X^2+X+1)$ is generated by $X$ and $X^1 + X^2 = X^3$.

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I don't think you can tell, in general. A finite field may have many generators, and it is possible that for generators $f$ and $g$ we have $1+f=f^i$ and $1+g=g^j$ with $i\ne j$. Perhaps you could try to find an example of this phenomenon.