Question

Find the constant sum for an ellipse with foci F1 (0, -8) and F2 (0, 8) and the point on the ellipse (0, 10). The constant sum is: ____. Enter only a number.

Answer 1

Eyeball Problem.

F1 and F2 are the Foci. They are oriented int eh y-direction.
This makes (0,10) a Major Vertex.
The Focal Length (the mysterious constant sum), is the length of the Major Axis.

2*10 = 20

If you like, you can calculate the distance from (0,10) to the two foci and add them up!