Chapter 4 - 4.3 - Conics - 4.3 Exercises - Page 337: 28

$y^2=-18x$ Focus: $(p,0)=(-\frac{9}{2},0)$

Parabola in the standard form with the vertex at origin (horizontal axis): $y^2=4px$ $6^2=4p(-2)$ $36=-8p$ $p=\frac{36}{-8}=-\frac{9}{2}$ $y^2=4(-\frac{9}{2})x$ $y^2=-18x$ Focus: $(p,0)=(-\frac{9}{2},0)$