power2

(x + y) ^ - (n - 3)

W3C sample	WIRIS
	$(x+y)^{-(n-3)}$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <apply>
    <power/>
    <apply>
      <plus/>
      <ci>x</ci>
      <ci>y</ci>
    </apply>
    <apply>
      <minus/>
      <apply>
        <minus/>
        <cn>n</cn>
        <cn>3</cn>
      </apply>
    </apply>
  </apply>
</math>

Author: Design Science, Inc. (E. Cannon, E. Tabacman, R.Miner)