Find the vertex, focus, and directrix of the following parabola. Then draw the graph.
(x – 2)2 = -3 (y + 1)
The two standard forms of the equation for a parabola are (x – h)2 = 4p(y – k) or
(y – k)2 = 4p(x – k).
Since the parabola is already in one of the standard forms, you can determine the values of h, k, and p, and form these values determine the vertex, focus, and directrix.
h = 2, k = -1, and p = –
Remember, for a parabola written in the form (x – h)2 = 4p(y – k), the vertex is (h , k).
Thus , the vertex of this parabola is (2,-1).
The axis of symmetry is vertical. The focus is – units away from the vertex, in the direction of the axis of symmetry.
Thus, it will be units below the vertex.
The focus is (2,-).
The directrix will be units above the vertex.
The equation for the directrix is
y = –
With this information, graph the parabola. First, graph the vertex, focus, and axis of symmetry.
Next, fill in the graph of the parabola.