title: Numpy.linalg.det() returns incorrect result
body: <p>Would anyone know why Numpy is returning "-2.0000000000000004" instead of "-2" for </p>
  
  <pre><code>&gt;&gt;&gt; M = [[1,2],[3,4]]
  &gt;&gt;&gt; numpy.linalg.det(M)
  -2.0000000000000004
  </code></pre>
  
  <p>I am using Python 3.4.2 (x64), Numpy 1.9.1 and Windows 7 x64.</p>