If the co-ordinates of two points A and B are ( 7 , 0 ) and ( - 7 , 0 ) respectively and P is any point on…

If the co-ordinates of two points A and B are (7,0) and  (-7,0) respectively and P is any point on the conic, 9x2+16y2=144, then PA+PB is equal to :
  1. 16
  2. 8
  3. 6
  4. 9

Solution

For ellipse x216+y29=1

Comparing with, standard equation of ellipse x2a2+y2b2=1, we get  

a=4,b=3.

e=1-916=74
Since, A and B are foci

Therefore, PA+PB=2a

=2×4=8.

Asked in: JEE Main 2020 (05 Sep Shift 1)

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