is the distance of z to 1.
is the distance of z to -i.
So you have the sum of two is less than or equal 2.
Thanks. I am still a bit confused. I understand that the definition of an ellipse is that the sum of the distances from both foci to a point is constant, but how would you know this in this example, without testing 2 points on the ellipse, to see if the sum of their distances from both foci are equal?