Answer:
Step-by-step explanation:
Please write this as y = (-1/12)(x - 4)^2 +2.
Compare this to y = 4p(x - h)^2 + k. (h, k) represents the vertex. Here the vertex is (4, 2).
Note that (-1/12) corresponds to 4p, where p is the distance between the focus and the vertex and also the distance between the focus and the directrix. If (-1/12) = 4p, then p = -1/48. Because p is negative the parabola opens down.
To find the equation of the directrix, add p to the vertex x-coordinate:
Equation of directrix: x = 4 1/12
Focus: x = 4 - 1/12 = 3 11/12
