I would post on the Physics help forum, but Latex does not work there! Perhaps a mathematician needs to help them out?

My text asks me to obtain the Lienard-Wiechert Potentials. The potentials are quoted as:

$\displaystyle \phi= \left[\frac q {r(1+u_r/c)}\right]_{ret}$ and $\displaystyle \underline w= \left[\frac {q \underline u} {r(1+u_r/c)}\right]_{ret}$

This seems wrong to me, I get the following

$\displaystyle \underline w= \left[\frac {q \underline u/c} {r(1+u_r/c)}\right]_{ret}$

Is my text incorrect?