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=2a Or a=9. Putting the value of a in the first equation, we get e=‌