## Precalculus (6th Edition) Blitzer

focus $(-3,0)$, directrix $x=3$ See graph.
Step 1. Given $y^2=-12x$, we have $4p=-12$ and $p=-3$ with the parabola opening to the left and vertex at $(0,0)$. Step 2. We can find the focus at $(-3,0)$ and directrix as $x=3$ Step 3. We can graph the parabola as shown in the figure.