Question

What is the equation of the parabola with a focus at (-3, 0) and a directrix x = 3.

Answer 1

i got y=1/12 x^2

Answer 2

am i right???

Answer 3

since the diretrix is at x=3 it means parabola is horizontal and opening to the left.

Answer 4

your answer is vertical parabola opening up

Answer 5

@myko thanks! what would it be so i can check it.

Answer 6

for horizontal parabola just exchenge x and y and use this:
equation for the parabola with the focus (0, p) and directex y = -p is y = 1/4p x2
which is equation of parabola with vertex at (0,0)
so later use translation to move it to (-3,0)

Answer 7

y=1/12 x^2 @myko

Answer 8

\[x=ay ^{2}\]
x=3=-1/(4a)
12a=-1
a=-1/12
so:
\[x=-1/12y ^{2}\]