title: matlab sum(X-Y) vs sum(X) - sum(Y)
body: <p>If we have two matrices <code>X</code> and <code>Y</code>, both two-dimensional, now mathematically we can say: <code>sum(X-Y)=sum(X)-sum(Y)</code>.</p>
  
  <p>Which is more efficient in Matlab? Which is faster?</p>