Question

PLEASE HELP.
Find the standard form of the equation of the parabola with a focus at (7, 0) and a directrix at x = -7

a. y 1/28 = x^2
b. x 1/28 = y^2
c. -28y = x^2

Answer 1

conic sections

Answer 2

find the vertex

Answer 3

is there a picture

Answer 4

There is no picture given.

Answer 5

Focus-directrix definition is a wonderful thing.

Locus of points Equidistant from a given focus and a given directrix.

How far are points from (7,0)? \(\sqrt{(x-7)^{2}+y^{2}}\)

How far are points from x = -7? \(|x-(-7)| = |x+7|\)

That's all you need. Just a little algebra to go!

Answer 6

You can also just jump right to the vertex.

(7,0) and x = -7 says clearly that the vertex is (0,0). Just draw in the axis of symmetry and you will see it.

Answer 7

So it'd be x 1/28 = y^2 because it's on the x-axis?

Answer 8

Wait I mean y 1/28 = x^2

Answer 9

right choice is not on the list

Answer 10

i think it's\[\sqrt{(x-7)^{2}+(y-0)^{2}} = \sqrt{(y+7)^{2}}\]

Answer 11

y2 = 14x?

Answer 12

Is that right? @sourwing

Answer 13

now a little algebra is used

Answer 14

How so? @faisalalif1999

Answer 15

one xec

Answer 16

Okay

Answer 17

y^2 = 28x

Answer 18

I showed you how to do this already

Answer 19

Haha sorry, I wasn't convinced that you were right. Thanks.

Answer 20

yw

Answer 21

cwrw238 is right

Answer 22

Thanks

Answer 23

What is a directrix?

Answer 24

http://www.mathwords.com/d/directrix_parabola.htm

- will tell you about the directrix

Answer 25

Thanks a ton! I appreciate this!