Which equation gives the directrix of y - 1/12x^2 - 5?

Answers

Answer #1 | 05/01 2014 11:45

I think you mean't to write the equation as: y = (1/12)x^2 - 5
Which can be rewritten as: (1/12)x^2 = y + 5 or x^2 = 12(y + 5)
This equation is of the standard form: (x-h)^2 = 4py, with (h,k) being the (x,y) coordinates of the vertex.
For given equation:
Vertex: (0,-5)
Axis of symmetry: x=0 or y-axis (parabola opens upwards).
4p = 12
p = 3
The directrix is p units below the vertex on the axis of symmetry.
Equation of Directrix: y = -8
Hope this helps! (:

Answer #1| 05/01 2014 11:45