Question

Please help me solve this: I need to find the quadratic equation of a parabola with a focus of (1, 3) and a directrix of y = -3.

Answer 1

eh i thought we solved it, lol , wasnt dat correct :S

Answer 2

Please, someone help me. I've been on this test for an hour and I'm about to cry. x_x

Answer 3

say (x, y) is some point on the parabola

Answer 4

@CyberShadow that was a different question. :/

Answer 5

by definition,
distance between any point on parabola and Focus = distance between Focus and directrix

Answer 6

@beccaboo022a Is there a formula I can use to input values? I know there's one that's something like y = (___)^2 + __

Answer 7

Would the point between the focus and directrix be the vertex?

Answer 8

yes there is a formula if u prefer formula to actually solving

Answer 9

Look, here's the actual question:

Answer 10

I can use the y = formula right? I jsut can't find the name of that formula and I don't remember what it was called. -____-

Answer 11

y = 4ax

Answer 12

*y^2

Answer 13

if dats the one u r talking abt? :S

Answer 14

an example equation would be y = 1/4(x-1)^2 + 2.

What is the name of this formula and how can I input the directrix and focus into that to get it like that?

Answer 15

I have to leave in 30 minutes and I've already been stuck on this question for 30. :/

Answer 16

see we have to find vertex first that wud be midway of directrix and focus

Answer 17

Would the vertex be (1, 0)?

Answer 18

yea

Answer 19

now just use this equation of parabola

Answer 20

Can you tell me the name of this formula? y = 1/4(x-1)^2 + 2
so i can find the real formula with the letters or w/e

Answer 21

Wait, I found it. y = a(x - h)^2 + k

Answer 22

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

Answer 23

yes!!

Answer 24

so now its solved!

Answer 25

Are they asking for a specific formula in the question? i can't afford to get it wrong :/

Answer 26

nope, they are just asking u find the equation of quadratic

Answer 27

Okay, so I can use the y = a(x - h)^2 + k?

Answer 28

formula is basically this -(y-h) = 4a(x-k)^2 equation of parabola

Answer 29

First figure out which direction the quadratic faces ?

Answer 30

then u can solve it and rearrange it

Answer 31

left/right

or

up/down

?

Answer 32

How do I find that out? And why can't I just use y = a(x - h)^2 + k? D:

Answer 33

once u figure that out, look at the attached chart

Answer 34

I don't know how to find a..

Answer 35

to figure out which direction it faces : look at the directrix

Answer 36

@beccaboo022a you're moving way too fast for me. :/

Answer 37

a is distance between directrix and vertex

Answer 38

that's 6 points

Answer 39

The focus it ouside and the directrix is in, right?

Answer 40

its right handed parabola as vertex is (1,0)

Answer 41

Alright ! draw the directrix and focus first

Answer 42

Wait, I'm cmixed up. The directrix is outside and the focus is inside.

Answer 43

draw it out

Answer 44

yeah rite Jay

Answer 45

Which means that the parabola looks like a smiley face.

Answer 46

draw it out