Here are some important formulae for PARABOLA which can help a lot in this topic............................

                                                                       When equation is y^2 = 4ax

coordinates of vertex = (0,0)

coordinates of focus= (a,0)

Equation of the directrix => x =-a

Equation of the axis = y = 0

Length of the latus rectum = 4a

Focal distance of a point P ( x,y) = a+x

                                                                         When equation is y^2 = -4ax

Coordinates of the vertex = (0,0)

coordinates of the focus = ( -a,0)

equation of the directrix = x = a

equation of the axis = y = 0

Length of the latus rectum = 4a

Focal distance of a point P (x,y) = a-x

                                                                                   When equation is x^2 = 4ay

Coordinates of vertex = (0,0)

coordinates of focus = (0,a)

equation of the directrix = y = -a

Equation of the axis = x = 0

Length of the latus rectum = 4a

Focal distance of a point P (x,y) = a+y

                                                                        When equation is x^2 = -4ay

Coordinates of vertex = (0,0)

Coordinates of the focus = ( 0,-a)

Equation of the directrix = y = a

Equation of the axis = x = 0

Length of the latus rectum = 4a

Focal distance of a point P (x,y) = a-y

I hope this will help a lot to the readers..................and they'll  find it quite easier.........