Display:

$x^2\searrow a^2$

Source:

<apply>
     <tendsto type="above"/>
     <apply>
          <power/>
          <ci> x </ci>
          <cn> 2 </cn>
     </apply>
     <apply>
          <power/>
          <ci> a </ci>
          <cn> 2 </cn>
     </apply>
</apply>