title: Solve system of non-linear equations in python
body: <p>Trying to solve a system of nonlinear equations and don't know which python solver to use.</p>
  
  <pre><code>a=Q1**2+Q4**2
  b=2*Q1*Q2-2*Q3*Q4
  c=2*Q1*Q3+2*Q2*Q4
  d=Q2**2+Q3**2
  </code></pre>
  
  <p><code>a,b,c,d</code> are just real numbers and <code>Q1,Q2,Q3,Q4</code> are the variables I want.</p>