Chapter 11: Parametric Equations and Polar Coordinates - Section 11.6 - Conic Sections - Exercises 11.6 - Page 677: 2

$y^{2}=-4x$ Focus$:\qquad (-1,0)$ Directrix is: $\qquad x=1$

The parabola opens to the left: $\quad\Rightarrow \quad y^{2}=-4px.$ The only equation of this form is $y^{2}=-4x=-4(1)x,\qquad\Rightarrow p=1$ Focus is at $(-p,0)=(-1,0)$ The directrix is: $\qquad $ $x=p$ $x=1$