The standard equation of an ellipse is:
(x-h)²/a² + (y-k)²/b² = 1
Since the center at the origin, then h = k = 0
The height of this ellipse = 8 units and the width = 4 units, that means the major axis is b (=8) and the minor axis is a (=4)
Then the equation becomes:
x²/16 + y²/64 = 1