In a system of equations with nine equations and nine unknown elements of the degree of three has been solved numerically with Mathematica software. In this method the roots are numerous, it is difficult to recognize the right roots.Can we solve these equations in a more confident way ?

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    $\begingroup$ What do you mean with "the right roots"? $\endgroup$ – Florian Aug 30 '18 at 10:59
  • $\begingroup$ Thank you for your answer,the root that makes the equations zero. In general , how can a root be chosen from the roots obtained ? $\endgroup$ – anousheh Aug 30 '18 at 11:12
  • $\begingroup$ For a system of nonlinear equations you may get more than one solution, i.e., more than one set of roots where all equations are zero. This means there may not be one unique solution. In that case, all solutions are equally correct and there is no reason to favor one over the other. If you want to restore uniqueness you may need to pose additional constraints, motivated from your application. $\endgroup$ – Florian Aug 30 '18 at 11:25
  • $\begingroup$ The answer was very complete ,thank you.How to solve a system of (a large number of) nonlinear simultaneous equations using MATLAB? Which software is better than Matlab or Mathematica? $\endgroup$ – anousheh Sep 2 '18 at 7:53
  • $\begingroup$ I have a system of nine nonlinear equations with nine variables to solve in Mathematica.First I used Solve[sys,var] which did not work and also NSolve did not work and by the use of findroot, numerous roots are obtained. How can I make it work? Is there another way of solving this ? $\endgroup$ – anousheh Sep 2 '18 at 9:18

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