This calls for a numerical approach. Using a simple derivative-free method (Nelder-Mead) might be enough. In Matlab this is implemented as "fmins". Redo the computation a number of times to see if the solution depends on the start data (there may be more than one solution for such a problem).Originally Posted byroeppieroeppie

A fancier method would be a Gauss-Newton method - it requires more programming, however.