title: Solving a system of equations programmably?
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/2474432/system-of-linear-equations-in-c">System of linear equations in C++?</a>  </p>
  </blockquote>
  
  
  
  <p>I have the following 2 systems of equations:</p>
  
  <p>For a,b,c,d:</p>
  
  <pre><code>0 = a * r1_x + b * r1_x * r1_y + c * r1_y + d
  1 = a * r2_x + b * r2_x * r2_y + c * r2_y + d
  0 = a * r3_x + b * r3_x * r3_y + c * r3_y + d
  1 = a * r4_x + b * r4_x * r4_y + c * r4_y + d
  </code></pre>
  
  <p>For e,f,g,h:</p>
  
  <pre><code>0 = e * r1_x + f * r1_x * r1_y + g * r1_y + h
  0 = e * r2_x + f * r2_x * r2_y + g * r2_y + h
  1 = e * r3_x + f * r3_x * r3_y + g * r3_y + h
  1 = e * r4_x + f * r4_x * r4_y + g * r4_y + h
  </code></pre>
  
  <p>I know the values of r1_x, r1_y, r2_x, r2_y, r3_x, r3_y, r4_x, r4_y, 
  and need to solve for a,b,c,d in the first one, and ,e,f,g, h in the second.</p>
  
  <p>I know how I would solve these with pencil and paper, but I'm really unsure how to program it. How could I solve the above equations in C or C++ (or psuedocode).</p>
  
  <p>Thanks</p>