matlab - how to plot ellipse in this format? -

I would like to ask how to ellipse in such a format:

An x ^ 2 + b y ^ 2 + c x y + d x + e y-1 = 0

I tried Explosive and Contour and it does not seem to work.

If you use that equation, then you have to complete the relationship c ^ 2 - 4ab & Lt; For 0 this is an ellipse.

EDIT: This clearly specifies how it does not work (what you were expecting and what happened) can be useful.