Algebra
posted by Natalia on .
Thanks to those who helped with my question: y+3=1/12(x1)^2. The only thing I am still unsure of is how to write the equation for the directrix. Do I just simply write 0=33, (the values plugged in for y=kp). Thanks again for your help!!

Whoops 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)

p = 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 
The form is
(xh)^2 = 4 a (yk)
here
(x1)^2 = 12 (y+3)
so 4 a = 12
a = 3
vertex to focus = a = 3
so focus at 33 = 6 so (1,6)
directrix is horizontal line a units above vertex so it is the line y = 0