$h = - vt + \frac{1}{2}g{t^2}$
$ \Rightarrow g{t^2} - 2vt - 2h = 0$
$ \Rightarrow t = \frac{{2v \pm \sqrt {4{v^2} + 8gh} }}{{2g}}$
$ \Rightarrow t = \frac{v}{g}\left[ {1 + \sqrt {1 + \frac{{2gh}}{{{v^2}}}} } \right]$
$\begin{array}{|c|c|c|c|c|} \hline t( s ) & 0 & 1 & 2 & 3 \\ \hline x ( m ) & -2 & 0 & 6 & 16 \\ \hline \end{array} $
($g = 9.8\,m/{s^2}$)