Posted by **samantha** on Sunday, June 15, 2008 at 7:35pm.

6. Find the equation of each parabola described below.

a) parabola with vertex (0,0) and the focus (0,7)

b) parabola with focus (-3,0) and directrix x=3

c) parabola with vertex (3,3) and directrix x=-1

d) parabola with focus (-2,-1) and directrix y=5

e) ysquared=-6x translated according to ((x,y) -->(x-2,y+4))

could someone help me with these??

- algebra -
**Damon**, Sunday, June 15, 2008 at 9:27pm
You need to know the following:

vertex at (h,k)

if it opens up or down:

4 a (y-k) = (x-h)^2

a negative a opens down

if it opens right or left:

4 a (x-h) = (y-k)^2

a negative a opens left

distance vertex to focus = a

distance vertex to directrix = a

ALWAYS SKETCH THEM

================================

for example a is vertex (0,0) so h = k = 0 and focus (0,7)

the sketch shows it with axis along the y axis opening up and distance a = 7

so

4 * 7 * y = x^2

or y = x^2/28

- algebra -
**Damon**, Sunday, June 15, 2008 at 9:29pm
Note that the vertex is halfway between the focus and the directrix by the way.

## Answer this Question

## Related Questions

- maths - Given that the equation of the parabola is 5y^2 + 24x = 0. Find (1)The ...
- Pre Cal - write the equations of the parabola, the directrix, and the axis of ...
- Algebra - Can someone tell me if I am right? I need to find the equation of a ...
- algebra problem - I need to find the equation of a parabola. I am not sure if ...
- Math - determine vertex, focus and directrix of parabola. then graph the ...
- Math - Find the vertex, focus, and directrix of the parabola. x^2 - 2x + 8y + 9...
- Vertex, Focus, & Directrix of Parabolas - Find the Vertex, Focus, and Directrix ...
- Math - determine vertex, focus and directrix of parabola. then graph the ...
- math - determine vertex, focus and directrix of parabola. then graph the ...
- Math - determine vertex, focus and directrix of parabola. then graph the ...