Answer
Focus: $(-\displaystyle \frac{1}{12},0)\quad$ Directrix: $x=\displaystyle \frac{1}{12}$
Work Step by Step
$x=-3y^{2}$
$y^{2}=(-\displaystyle \frac{1}{3})x$
$ y^{2}=-4px \quad \Rightarrow \quad$ the parabola opens left,
$y^{2}=4(-\displaystyle \frac{1}{3\cdot 4})x$
$y^{2}=-4(\displaystyle \frac{1}{12})x\quad \Rightarrow \quad p=\frac{1}{12}$
Focus: $(-\displaystyle \frac{1}{12},0)\quad$ Directrix: $x=\displaystyle \frac{1}{12}$
