title: How to make Mathematica Simplify Square Root Expression
body: <p>I would like Mathematica to evaluate square root of a squared variable.  Instead it is just returning the squared variable under square root.  I wrote a simple code as an example:</p>
  
  <pre><code>x = y^2
  z = FullSimplify[Sqrt[x]]
  </code></pre>
  
  <p>But it is returning y^2 under a square root sign!</p>