Find the focus of the parabola.

Question

The vertex of a parabola is (10,−9). The directrix is the line y=−10. Find the focus of the parabola.

Answer 1

vertex (10,-9) and directrix y=-10

the focus is the same distance to the vertex as the distance from vertex to the directrix

focus is (10, -8), which is 1 unit from the vertex. the vertex is one unit from the directrix