Slightly nicer

comment.md

The original source is on wikipedia. Unicode and named entities are used instead of hex entities with comments. (A unicode character could also have been used for InvisibleTimes, but it would not be readable.)

quadratic.xml

<math mode="display" xmlns="http://www.w3.org/1998/Math/MathML">
  <semantics>
    <mrow>
      <mi>x</mi>
      <mo>=</mo>
      <mfrac>
        <mrow>
          <mo form="prefix">−</mo>
          <mi>b</mi>
          <mo>±</mo>
          <msqrt>
            <msup>
              <mi>b</mi>
              <mn>2</mn>
            </msup>
            <mo>−</mo>
            <mn>4</mn>
            <mo>&InvisibleTimes;</mo>
            <mi>a</mi>
            <mo>&InvisibleTimes;</mo>
            <mi>c</mi>
          </msqrt>
        </mrow>
        <mrow>
          <mn>2</mn>
          <mo>&InvisibleTimes;</mo>
          <mi>a</mi>
        </mrow>
      </mfrac>
    </mrow>
    <annotation encoding="TeX">
      x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}
    </annotation>
    <annotation encoding="StarMath 5.0">
      x={-b plusminus sqrt {b^2 - 4 ac}} over {2 a}
    </annotation>
  </semantics>
</math>