10-2. Parabola, Ellipse, Hyperbola
medium

If the co-ordinates of two points $A$ and $B$ are $(\sqrt{7}, 0)$ and $(-\sqrt{7}, 0)$ respectively and $P$ is any point on the conic, $9 x^{2}+16 y^{2}=144,$ then $PA + PB$ is equal to

A

$8$

B

$6$

C

$16$

D

$9$

(JEE MAIN-2020)

Solution

$\frac{x^{2}}{16}+\frac{y^{2}}{9}=1$

$a =4 ; b =3 ; e =\sqrt{\frac{16-9}{16}}=\frac{\sqrt{7}}{4}$

A and $B$ are foci

$\Rightarrow PA + PB =2 a =2 \times 4=8$

Standard 11
Mathematics

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