Consider the parabola with focus (-p, 0) and directrix x = p. (Assume p 0.)
a. Toward which direction does the parabola open?
b. How does the parabola change as p increases?

Question

Consider the parabola with focus (-p, 0) and directrix x = p. (Assume p> 0.)
            a. Toward which direction does the parabola open?
            b. How does the parabola change as p increases?

mertsj · Answer

The parabola opens down because it cannot cross it's directrix and the focus is inside the parabola.

anonymous · Answer

i thought it opened to the right..

mertsj · Answer

I see now.  The directrix is vertical but the focus is (-p,0) so it opens to the left.

mertsj · Answer

|dw:1326313382457:dw|