Question

What are the focus and directrix of the parabola with the equation y=1/12 x^2

Answer 1

Answer:

$\boxed{y=-3}$

Step-by-step explanation:

The graph of this parabola is shown below. From this graph we know that:

VERTEX:

$(h,k)=(0,0)$

DIRECTIX:

Since the vertex lies on the origin and the parabola opens upward, then the standard form of this parabola is:

$x^2=4py$

So:

$y=\frac{1}{12}x^2 \\ \\ \therefore 12y=x^2 \ or \ x^2=12y \\ \\ \\ Then: \\ \\ 4p=12 \therefore p=3$

Then the directrix is:

$y=k-p \\ \\ \therefore y=0-3 \therefore \boxed{y=-3}$