#tex{{{
\frac{dv}{dt} & = g - \frac{\kappa}{m} v^2 \\
\frac{dv}{dt} & = g(1-k^2 v^2) \ \ \left(\frac{\kappa}{mg} \equiv k^2 \right)
}}}
#tex{{{
-\frac{\hbar}{i}\frac{\partial \psi}{\partial t} = -\frac{\hbar2}{2m} \triangle \psi
}}}
&tex{b+x};