Question

Find the standard form of the equation of the parabola with a focus at (-7, 0) and a directrix at x = 7. @jim_thompson5910
I'm not sure what to do, can you help?

Answer 1

what's the distance from the focus to the directrix?

Answer 2

um i'm not sure. @jim_thompson5910

Answer 3

plot it out

Answer 4

plot the line x = 7 and the point (-7,0)

Answer 5

14?

Answer 6

yep

Answer 7

cut that in half to get 14/2 = 7

Answer 8

so the focal distance is 7 units, which means p = 7

Answer 9

the vertex will lie on the midpoint of (7,0) and (-7,0)

what is the vertex?

Answer 10

0,0?

Answer 11

@jim_thompson5910

Answer 12

so (h,k) = (0,0)

Answer 13

h = 0
k =0

Answer 14

since the directrix is a vertical line, and because the focus is to the left of the directrix, we know the parabola opens up to the left

Answer 15

so it's of the form

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

in this case

p = 7
h = 0
k = 0

making our equation to be

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

-4*7(x-0) = (y-0)^2

-28x = y^2

y^2 = -28x

Answer 16

you can also write the equation as y^2 + 28x = 0

Answer 17

the only one i have with the anser y^2 is y2 = -14x the other answers are x = -(1/28)y^2
-28y = x2
y = -(1/28)x^2
@jim_thompson5910

Answer 18

hmm there has to be a typo then

Answer 19

I don't see any other equivalent answers

Answer 20

oh wait

Answer 21

y^2 = -28x

-28x = y^2

x = (-1/28)y^2

Answer 22

Find an equation in standard form for the ellipse with the vertical major axis of length 16, and minor axis of length 4.
@jim_thompson5910

Answer 23

what did you get

Answer 24

the one you found

Answer 25

what did I find?

Answer 26

x = (-1/28)y^2

Answer 27

that was the last problem

Answer 28

and that's not even an ellipse

Answer 29

yeah can you help me with this new one?

Answer 30

what did you get for this new one

Answer 31

i don't konw what to do?

Answer 32

check your notes or go back to the lesson

Answer 33

ok