We know that distance between the foci is 2ae and sum of the distances from any point on the ellipse from the two foci is 2a.Hence(12−4)2+(5−3)2​=2ae⇒ae=17​⋯(1)Also PS+PS′=2a, here P is origin as the ellipse passes through origin.⇒122+52​+42+32​=2aOr a=9. Putting the value of a in the first equation, we get e=917​​.