Question

A parabola has its vertex at (2, 2), and the equation of its directrix is y = 2.5. The equation that represents the parabola is

Answer 1

We are given with the data of a parabola with vertex at (2, 2) and directrix at y  = 2.5. the formua should be ax^2 + b x + c = y because of the directrix. 

(x-h)^2 = 4a (y-k)
(x-2)^2 =4a (y-2) 
a is the equidistant distance from focus to vertex and from vertex to directrix that is equal to -0.5
then the  answer is 
(x-2)^2 =-0.5*4 (y-2) 
x2 - 4x + 4 = -2y +4
x2-4x+2y = 0

answer is C