Question

who knows the equation of a parabola with a vertex (0,5) and a directrix=8

Answer 1

Find the equation of the parabola given vertex at (5, 0) and y = -8 as dirctrix.

The axis of symmetry is parallel to the Y –axis. The equation for the directrix is y = k – p. Substituting k = 0 and y = -8 to the equation :

-8 = 0 – p

-8 = -p

8 = p or p = 8

Therefore the equation of the parabola we are looking for is :

(x – 5 ) ^ 2 = 8y

Answer 2

thanks but the vertex was at (0,5) not (5,)

Answer 3

not (5,0)

Answer 4

Since the directrix is vertical, that means this is a sideways parabola (the quadratic term is y)

Answer 5

the equation should be 4p(x-h) = (y-k)^2

Answer 6

p=3
h=0
k=5
so the equation is 12x = (y-5)^2

Answer 7

okay thanks. i have four answers they are: x=32(y-5)^2, y=1/32(x+8)^2, x=-1/32(y-5)^2, or

Answer 8

this is on a multiple choice hw

Answer 9

sorry p=8
so the answer is 32x=(y-5)^2

Answer 10

thanks

Answer 11

sorry again... p=-8
so the equation is -32x=(y-5)^2
choose the equivalent equation in your multiple choice,...

Answer 12

is directrix at x=8 or y=8?

Answer 13

haha... i didn't even see that "directrix=8"

Answer 14

I assumed x=8