_
x - intercepts: ±Ö6
                   _     
y - intercepts: ±2Ö3
Plot those 4 intercepts:
 draw the ellipse 
Since it looks like this: "
" 
and not like this:"
",
its equation is
 + 
 = 1
The center is (h,k) = (0,0), so it has the form
 + 
 = 1
 + 
 = 1
The y-intercepts are the vertices, the x-intercepts are the covertices:
                                                               _
a = semi-major axis = distance between center and a vertex = 2Ö3
Therefore 
                                                                _
b = semi-minor axis = distance between center and a covertex = Ö6
                  _                       _
Therefore a² = (2Ö3)² = 4·3 = 12,  b² = (Ö6)² = 6
 + 
 = 1
Edwin