Question

Write an equation for the parabola with vertex (3, -6) and focus at (3, -4).

Answer 1

There will be a point on the directrix such that the mid point of he focus and the point on directrix is the vertex.
Then you will get the equation of directrix.
Then the distance from directrix to any arbitrary point on the parabola is equal to the distance from the focus to the arbitrary point. This gives you the equation of the parabola