Ellipse 1 Question 6

7. If $P=(x, y), F _1=(3,0), F _2=(-3,0)$ and $16 x^{2}+25 y^{2}=400$, then $P F _1+P F _2$ equals $(1998,2 M)$

(a) 8

(b) 6

(c) 10

(d) 12

Objective Questions II (Only one or More than one)

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Answer:

Correct Answer: 7. (c)

Solution:

  1. Given, $16 x^{2}+25 y^{2}=400$

[given]

$\Rightarrow \quad \frac{x^{2}}{25}+\frac{y^{2}}{16}=1$

Now, $\quad P F _1+P F _2=$ Major axis $=2 a$

$ =2 \times 5=10 $

[where, $a=5$ ]



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