What is the equation of the ellipse with foci (5, 0), (-5, 0) and co-vertices (0, 4), (0, - 4) ?

The curve equation y3 + 3yx - x3 = 9

Differentiate implicitly with respect to x.

3y2 (dy/dx) + 3[y + x (dy/dx) ] - 3x2 = 0

3y2 (dy/dx) + 3y + 3x (dy/dx) ] = 3x2

(dy/dx) (3y2 + 3x) = 3x2 - 3y

dy/dx = 3 (x2 - y) / 3 (y2 + x)

dy/dx = (x2 - y) / (y2 + x)