Set Up MathJax

Include this text somewhere in your document. MathJax recommends to placing it in the HTML header, but it may also appear in the body of the document.

<script type="text/javascript" async 
  src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/latest.js?config=TeX-MML-AM_CHTML">
</script>

For comprehensive documentation see the MathJax website

MathML

MathML code looks like this:

<p>
When
<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mi>a</mi><mo>&#x2260;</mo><mn>0</mn>
</math>,
there are two solutions to
<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mi>a</mi><msup><mi>x</mi><mn>2</mn></msup>
  <mo>+</mo> <mi>b</mi><mi>x</mi>
  <mo>+</mo> <mi>c</mi> <mo>=</mo> <mn>0</mn>
</math>
and they are
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mi>x</mi> <mo>=</mo>
  <mrow>
    <mfrac>
      <mrow>
        <mo>&#x2212;</mo>
        <mi>b</mi>
        <mo>&#x00B1;</mo>
        <msqrt>
          <msup><mi>b</mi><mn>2</mn></msup>
          <mo>&#x2212;</mo>
          <mn>4</mn><mi>a</mi><mi>c</mi>
        </msqrt>
      </mrow>
      <mrow>
        <mn>2</mn><mi>a</mi>
      </mrow>
    </mfrac>
  </mrow>
  <mtext>.</mtext>
</math>
</p>

The output looks like this:

When $a\ne 0$, there are two solutions to $a{x}^2+bx+c=0$ and they are $$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}\text{.}$$