Question 153
Find all non-empty sets $S$ of nonzero real numbers such that
a) $S$ has at most 5 elements;
b) If $x$ is in $S$, then so are $1-x$ and $\frac{1}{x}$.
a) $S$ has at most 5 elements;
b) If $x$ is in $S$, then so are $1-x$ and $\frac{1}{x}$.