As we have seen above, we need to insert the appropriate constant in the space provided on the left--hand side of the equation in order to make that side a perfect square. In this case, that quantity is 4. Thus, we arrive at
After some algebra, we see that this is the same as
or
Now we can ``read off'' the necessary information to solve this problem.
First, the vertex of this parabola is clearly 
. Next, since
and the axis of the parabola is horizontal,
I know that the focus must be located 3 units to the left of the vertex,
placing it at the point 
. Finally, the directrix is the vertical
line 3 units to the right of the vertex, which is the line
