This came up as the solution to a constrained optimization problem (after doing some analysis to find the stationary points of some Lagrangian): $$ A_{ij} \exp(\eta_j) = B_{ij} \exp(\eta_i) $$ $A$,$B$ are square of dimension $n\times n$. $B$ is known and we want to find $A$ and $\eta$ (the $n$-dim vector of lagrange multipliers).
Is there an analytic solution?