# What is the vertex form of the equation of the parabola with a focus at (1,-9) and a directrix of #y=-1 #?

##### 1 Answer

Apr 9, 2017

#### Explanation:

Parabola is the locus of a point which moves so that its distance from a point called **focus** and a line called **directrix** is always same.

Hence a point, say

As the distance from

or

or

or

or

or

Hence, vertex is

graph{(y+1/16(x-1)^2+5)(y+1)(x-1)((x-1)^2+(y+9)^2-0.04)=0 [-20.08, 19.92, -17.04, 2.96]}