How to find an equation of an ellipse?

Find the equation of an ellipse with the following.

$Center: (0,0)\ Focus: (3,0)\ Vertex: (-4,0)$

a is the distance from the origin of the ellipse c is the distance from the origin to the foci $ a = 4 $ $ c = 3 $ $ foci = (3,0), (-3,0) $ ${b}^{2} = {a}^{2}-{c}^{2}$ ${b}^{2} = {4}^{2}-{3}^{2}$ ${b}^{2} = 16-9$ ${b}^{2} = 7$

Remember the standard form of an ellipse?

$\frac { { x }^{ 2 } }{16} +\frac { { y }^{ 2 } }{ 7 } =1$