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 :
Solution
9x<sup>2</sup> + 16y<sup>2</sup> = 144
<br><br>$\Rightarrow$ ${{{x^2}} \over {16}} + {{{y^2}} \over 9} = 1$
<br><br>$\therefore$ a = 4; b = 3;
<br><br>Now e = $\sqrt {1 - {9 \over {16}}} = {{\sqrt 7 } \over 4}$
<br><br>A and B are foci
<br><br>PA + PB = 2a = 2 × 4 = 8
About this question
Subject: Mathematics · Chapter: Conic Sections · Topic: Parabola
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