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Ans: f(x) = (-1/16)*(x²) D.
how did you get that ?
If the focus is at (0,-4) and the directrix is y = 4 then the vertex of the parabola is midway between these two features at (0,0). The parabola is thus a downward opening parabola with the standard equation x² = 4cy where c is the distance from the vertex to the focus. In this question, c = -4.
is that the formula that you would use for all parabola equations?
@nono266 can you explain this better?
well it say's it's the standard equation. So i am assuming yes...
how do you know which one is 'C'
still need help!
ok! from the start.
yes how do you do that?
The parabola can look like
can u see that. @scenemunster
and please if u are interested in learning u must be interactive. or u can just have answers. @scenemunster It's up to you.
let's take a general form. suppose this figure.
this amkes no sense to me tbh
now, In this figure Point B is known as the vertex of the parabola, A is known as the focus, and line D is known as Directrix of the parabola.
where C is at the same distance from origin as is the focus of parabola.
has, it started making sense @scenemunster
great, The general equation of east facing parabola, whose vertex is at (0,0) is y^2 = 4ax
are you getting it.
where a is the distance from vertex to the focus of the parabola
as distance being a, and the for every positive x there will be two values of y one negative and the other positive , the parabola is sketched this way. i.e., east facing.
im so confused
the east facing parabola
TAKING THIS AS CONVENTION, ARE U COMFORTABLE NOW.
@scenemunster ??? please be quick! I don't have much time.
ok so a =4?
4 comes in general equation. they made the general equation this way
a is some constant which changes it's value according to question.
@amistre64 can you help as well. im sorry im naturally blonde and i dont know XD
so what is the equation like how do i set it up
Ok, leave that.
for your question.
let me make the figure.
where a =-4. y = -16x^2
focus of parabola (0,-4)
That means the answer is a
ok. i understand but y would it be a my guess was d
wait a second, it won't actually be A or D it would be C, reason, general equation, x^2 = -4by => x^2 = -16y, b=4 =>y =-x^2/16
ok. my besty said the same thing
@scenemunster , n sorry actually I was explaining the east one so by mistake I told u A earlier.
and, later we changed the direction of parabola to south and hence the equation changed. Sorry 'bout that but the answer is C for 100%
ok i got it thank you