If the co-ordinates of two points A and B
are \[\left( {\sqrt 7 ,0} \right)\] and \[\left( { - \sqrt 7 ,0} \right)\] respectively and
P is any
point on the conic, 9x2 + 16y2 = 144, then PA + PB is equal to :
Solutions · 1
Official solution
9x2 + 16y2 = 144
\[ \Rightarrow \] \[{{{x^2}} \over {16}} + {{{y^2}} \over 9} = 1\]
\[ \therefore \] a = 4; b = 3;
Now e = \[\sqrt {1 - {9 \over {16}}} = {{\sqrt 7 } \over 4}\]
A and B are foci
PA + PB = 2a = 2 \times 4 = 8