Question

Find the equation of a parabola with vertex at the origin and the directrix, y = 2. 

Answer 1

Let the equation of the directrix be y = a.       
a = 2
Equation of the parabola with directrix y =a is \[x^2 = - 4ay\] 

Hence, the required equation of the parabola is \[x^2 = - 8y\]