Question

Derive the equation of the parabola with a focus at (2, 4) and a directrix of y = 8.

Answer 1

f(x) = −1/8 (x − 2)2 + 6

f(x) = 1/8 (x − 2)2 + 6

f(x) = −1/8 (x + 2)2 + 8

f(x) = 1/8 (x + 2)2 + 8

Answer 2

@ganeshie8 @Haseeb96

Answer 3

look
The equation of a parabola with focus in (h,k+p) and directrix y=k-p, is,
(x−h)2=4p(y−k)
can you do the rest ?

Answer 4

whats h and k and p?

Answer 5

@pak

Answer 6

@paki

Answer 7

@Brainybeauty

Answer 8

I'm sorry I have not yet studied parabolas... :/

Answer 9

Oh okay, thanks for trying though @Brainybeauty

Answer 10

do you know the basics of parabola...?

Answer 11

:) Ur welcome. Do tag me in your other questions. I will try to solve them if I can! :)

Answer 12

No I don't @paki

Answer 13

have a look here please...


http://hotmath.com/hotmath_help/topics/finding-the-equation-of-a-parabola-given-focus-and-directrix.html

Answer 14

also here too...


http://www.algebra.com/algebra/homework/Quadratic-relations-and-conic-sections.faq.question.83012.html

Answer 15

f(x) = 1/8 (x + 2)2 + 8 ?

Answer 16

how... can you explain...?

Answer 17

This is not going anywhere, if you try to derive the equation of the parabola without knowing much about the concept "parabola".

Answer 18

Parabolas are because of quadratic equations. The values which solve quadratic equations make a parabola.

Answer 19

Yes, if the parabola opens up or down.

Answer 20

Yes. If x is negative, the parabola is a straight U and if it is positive it is an inverted U.

Answer 21

I gave up on the question. The joke was what type of shoes do ninjas wear? Sneakers @Brainybeauty @paki

Answer 22

Haha! That's funny XD

Answer 23

lol.... HEELS :)

Answer 24

But please try you will get it.
The value of x should be such that f(x) is equal to 8.

Answer 25

bacuase directrix of y=8 and y is usually the function of x so...

Answer 26

Brainybeauty, it is the other way, if ax²+bx+c=0 is with a positive a, then it opens up, and if a is a negative number than it opens down (and if a=0 then it is a line).

Answer 27

I don't know much about this topic, it hasn't been discussed in my school yet, but I'm just recalling what I heard some people say...

Answer 28

Yes, but it is good to remember,
a>0 opens up
a=0 line
a<0 opens down

Answer 29

Horizontal parabola is not a function.

Answer 30

Yesss! I get it now. Thx. :)

Answer 31

Anytime:) I myself a trig student. I know some things from calc 1 though....

Answer 32

Wow! I'm studying trigo too (basic and its difficulty is increasing). But I don't know anything about calculus. I just know bits about differentiation and limits. I am going to study it next year. @SolomonZelman