linebreakFrac

Handling very long fractions (600px width used for image). Second line should be centered.

<math xmlns="http://www.w3.org/1998/Math/MathML" indentalign="center" display="block">
  <mfrac>
    <mrow>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
      <mo>+</mo>
      <mi>x</mi>
    </mrow>
    <mrow>
      <mi>y</mi>
      <mo>+</mo>
      <mi>y</mi>
      <mo>+</mo>
      <mi>y</mi>
    </mrow>
  </mfrac>
</math>

Author: Design Science, Inc. (D. Doyle, R.Miner)