Is there a numerical method to solve this equation, considering that we cannot write out the specific expressions for F or G, but can numerically compute the gradient or function value information at a certain point x? Can anyone provide some suggestions? In regard to my specific problem, $F(x) = \frac{||f(x)||^2_2}{2}$. f(x) is a known function from $R^n$ to $R^n$. $G(x)=\frac{a}{x}+b$.
$a$ and $b$ are constant vectors, and the division operation is element-wise division.
I can also compute the function value of $f^{-1}(x)$, I'm not sure if this would be helpful.