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December 19, 2014

December 19, 2014

Posted by **Natalia** on Sunday, November 30, 2008 at 3:02pm.

- Algebra -
**Natalia**, Sunday, November 30, 2008 at 3:03pmWhoops and one thing I forgot. Is it allowed for a parobala to open upward and have the directrix intercept it? Since p is greater than zero, it would have to open upward, but then the directrix would intercept the parobala (the directrix follows the x axis, and is at zero y)

- Algebra -
**Damon**, Sunday, November 30, 2008 at 3:09pmp = Negative. (I called p a but same difference)

I showed you that this parabola opens downward in my explanation of the axis of symmetry at x = 1

the directrix is a horizontal line (m=0)

y = 0 x + 0

or

y = 0

- repeating that part -
**Damon**, Sunday, November 30, 2008 at 3:11pmThe form is

(x-h)^2 = 4 a (y-k)

here

(x-1)^2 = -12 (y+3)

so 4 a = -12

a = -3

vertex to focus = a = -3

so focus at -3-3 = -6 so (1,-6)

directrix is horizontal line a units above vertex so it is the line y = 0

- repeating that part -

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