Many biological systems give rise to optimization problems (for instance, when we have to identify the model or control of the system). Here, we propose a very simple method to find the extremum of a n‐variables function. This technique leads to the optimization of a one‐variable function. Our procedure can be applied to two kinds of cybernetic problems: resolution of equations with several variables and identification of the black box. It may also be used to solve optimal control problems arising from regulated or homeostatic systems. The technique gives a good approximation which may be used to seek a better solution.