Math help!

Question

Write the equation of the ellipse, if the distance between the focal points is 8 and the point M(15,-1) belongs to the ellipse. 

Answer 1

(x+1)^2/256 + (y+1)^2/84 = 1 which has foci (5,-1) and (-3,-1)

or

(x-31)^2/256 + (y+1)^2/84 = 1 which has foci (35,-1) and (27,-1)

are two main ellipses with foci 8 apart that have (15,-1) as a point

but there are an infinite number of other ellipses.