 of that function as
  well. If we want to first compute a partial with respect to $x$,
  and then with respect to $y$, we would use one of the following
  notations: $$f_{xy}=\ds\frac{\partial}{\partial
  y}\frac{\partial}{\partial x}f = \frac{\partial}{\partial
  y}\frac{\partial f}{\partial x} = \frac{\partial^2 f}{\partial y
  \partial x}.$$

  <div class="problem" label="Mixed Partials Agree" id="second-partials-agree">

    <div class="marginpar">
      <span class="larsonfive">See Larson 13.3:71&ndas