title: How to get the correct solution of this simple equation in wxMaxima?
body: <p>I am trying to solve the following simple equation in wxMaxima:</p>
  <p>21.3874=0.00202415/(d^3)</p>
  <p>When I use <code>solve()</code>, I get 3 solutions (2 complex and 1 real). I know that d is real and positive (because it's a diameter) so I'm only interested in the third solution. It's given in the following form:
  d=((40483)^(1/3))/(10427748^(1/3)) and I tried saving it with <code>map()</code> function but it saved all 3 solutions and I don't know how to map only the last one so that I can use it for further calculations.</p>
  <p>Anyway, after rewriting this solution and using <code>float()</code> function on it, the result is: 0.1571668
  But it's incorrect since the result should be 0.0455717.</p>
  <p>Interestingly, <code>to_poly_solve()</code> gives different solutions with the real one being: 0.2439467</p>
  <p>I have 3 questions regarding this problem:</p>
  <ol>
  <li>Why does wxMaxima give two incorrect solutions and how to get the right one ?</li>
  <li>How can I tell the Maxima that I am looking only for real and positive solution of a given equation.</li>
  <li>Is it possible to map selected solution so that it can be referenced in further calculations (for example to use <code>float()</code> on it) ?</li>
  </ol>