Chapter 10 - Parametric and Polar Curves - 10.4 Conic Sections - 10.4 Exercises - Page 750: 19

$${y^2} = 16x$$

$$\eqalign{ & {\text{The directrix is }}x = - 4,{\text{ then the parabola has the equation }}{y^2} = 4px \cr & {\text{With }}x = - p \cr & x = - p\,\,\, \Rightarrow \,\,\,\,\,p = 4 \cr & {\text{The equation of the parabola is:}} \cr & {y^2} = 4\left( 4 \right)x \cr & {y^2} = 16x \cr} $$