If I have 2 or more eqiations of degree 5, each representing a parametrr that I'd want to optimie. Say, one equation shows trend of production and the other one trend of rejections and both are function of $x$. Now I need a value of $x$ at which my system is optimized.
Meaning a value of $x$ for which production is maximized and rejection is minimized? Your answers will be appreciated.