What is the equation of the parabola with a focus at (-3,4) and a directrix of y= -7?
Because the directrix is a horizontal line, we know that the vertex has the same x coordinate as the focus and has a y coordinate that is the midpoint between the directrix and the focus:
Substitute the values for h and k into the vertex form for the equation of a parabola that opens vertically:
Compute the signed vertical distance,
We know that
Substitute the value for "a" into the equation: