<?xml version="1.0" encoding="UTF-8"?>

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mtext>Inline, auto, thick line </mtext> 
  <mstyle displaystyle="false" scriptlevel="0">
    <mrow>
      <mfrac linethickness="1pt">
        <mrow>
          <msup>
            <mi>x</mi> 
            <mn>2</mn> 
          </msup> 
          <mo form="infix">+</mo> 
          <mn>1</mn> 
        </mrow> 
        <mi>x</mi> 
      </mfrac> 
    </mrow> 
  </mstyle> 
  <mtext>, the superscripted 2 should be script-script size.</mtext> </math>