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Keep only positive and real solutions from Solve?

Posted 3 years ago
4 Replies
2 Total Likes

Hi people,

I have a problem where I get four solutions to an equation system. Two imaginary, one negative and one positive. Can I somehow automatically tell Mathematica to only keep the real and positive answer?

Sort of:

Solve[equation1==equation2, x]//Real//Positive

Thanks! //Freddy, Sweden

4 Replies

It would be useful to have a complete self-contained example. Anyway, could try equation1==equation2 && x>0 as first argument to Solve.


Solve[equation1==equation2&& x > 0, x, Reals] 


 Solve[{equation1==equation2, x > 0}, x, Reals] 


Thanks a bunch, people! =D

Posted 2 months ago

Hi everybody, I have the same question, but I have hundreds of variables in my system of equations.

In my large system of equations including numerous variables, I use the following structure:

      eq3==eq4&& ....]

and I do not specify any variable, so the solver tries to solve the system for all the variables.

Now the question is instead of this format:

      eq3==eq4&& ....&&, x1>0,x2>0,..., Reals] 

How can I ask the solver to return a non-zero positive solution for all the variables? Thanks

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