This is the equation of an ellipse. Divide through by 42: 3x^2/14+y^2/6=1.
The standard form of the ellipse is x^2/a^2+y^2/b^2=1 where a and b are the semi-major and semi-minor axes. Isolating y^2 gives us the length of the radius of the ellipse in the y direction, which is √6=2.45 approx. The y-radius is only a little bigger than the x-radius (approx 2.16).