# What is the vertex form of the equation of the parabola with a focus at (20,-10) and a directrix of #y=15 #?

##### 1 Answer

Aug 3, 2017

**Equation of parabola is**

#### Explanation:

Focus is at

Vertex is equidistant from focus and directrix and in midway

between them. So vertex is at

Equation of Parabola in vertex form is

opens downwards

vertex is

Hence equation of parabola is

graph{-1/50(x-20)^2+2.5 [-160, 160, -80, 80]}