Conic Sections - Parabolas - Chapter 11.1, Problem 3E

$y^2=4px$ is the equation for a parabola opening horizontally. We can observe from the example equation $y^2=12x$ that the coefficient of y is 12 To find the p value set $12=4p$ (This will allow you to find the focus and directrix of a parabola centered at the origin) Now solve for p $3=p$ To find the focus use the focus coordinates (p,0) Substitute: The focus is at (3,0) To find the directrix use the directrix formula $x=-p$ Substitute: The directrix is $x=-3$ Keep in mind these formulas and coordinates are for finding the directrix and focus when the parabola's vertex is at (0,0).