Define the function $f(x)=\frac{a}{1-x}$. If $f(-1)=f^{-1}(4a+1)$, find the product of all possible values of $a$.
Stop posting in unclear latex, actually convert to this site's latex so people can see more clearly.
\(f(x)=\frac{a}{1-x}\)
\(f(-1)=f^{-1}(4a+1)\)