ass="hl str">&quot;x&quot;</span><span class="hl std">)</span>
</pre></div>
<div class="output"><pre class="knitr r">  expression(((-t) * ((-s1) + (-t) * (2 * (-s1) + (-t) * (-t) * 
      (-2 * (-s1) - (-t) * (-s1)))) * px0 + (1 - t) * ((-s2) + 
      (1 - t) * (2 * (-s2) + (1 - t) * (8 - 12 * (-s2) + (1 - t) * 
          (14 * (-s2) - 11 + (1 - t) * (4 - 5 * (-s2)))))) * px1 + 
      t * ((-s1) + t * (2 * (-s1) + t * (8 - 12 * (-s1) + t * (14 * 
          (-s1) - 11 + t * (4 - 5 * (-s1)))))) * px2 + (t - 1