# Thread: [SOLVED] Directrix and Focus

1. ## [SOLVED] Directrix and Focus

If the Directrix is negative then the Focus will have a positive sign?

Example:

Directrix: $x=-5$ then Focus $(5,0)$

Am I right, or the sign remains the same?

2. This doesn't seem to always be true. The focus and directrix are equidistant from the vertex when connecting the three in a line. Consider a basic case where the standard parabola of y=x^2 was vertically shifted up 30 units. The focus is slightly above the vertex and the directrix is a horizontal line running slightly below the vertex but both are always positive.

3. I forgot to mention that the Vertex is (0,0). So, if the Vertex is at the Origin. Does this rule apply?

4. Originally Posted by looi76
I forgot to mention that the Vertex is (0,0). So, if the Vertex is at the Origin. Does this rule apply?
Yes it seems so to me, just remember one is a point and the other a line.