Equation and shape of the parabola

Author:
Mathguru
We can clearly see the graph of a parabola in red with focus at point A (blue) and directrix ‘a’ (green). Directrix ‘a’ is a line which passes through two points B and C. We can move the three points A, B and C. On moving any of the three points A, B and C we see that the size and position of the parabola gets altered