Q. If $( - 1,\ - 2\sqrt{2)}\$ is one of extremity of a focal chord of the parabola $y^{2} = - 8x,\ \$then the other extremity is

A) $( - 1,\ - \sqrt{2})$
B) $(\ 2\sqrt{2}\ , - 1)$
C) $( - 4,\ 4\sqrt{2})\$
D) $(4,\ 4\sqrt{2})$
Explanation

(c)
Given $y^{2} = - 8x$
Here, $a = - 2$
We know that if one end of a focal chord is $\left( at^{2},2at\ \right)$, then the other end will be $\left( \frac{a}{t^{2}}, - \frac{2a}{t} \right)$
Here, one end is $( - 1,\ 2\ \sqrt{2)}$
$\therefore\ at^{2} = - 1\ \Rightarrow \ t = \frac{1}{\sqrt{2}}$ $\lbrack\because a = - 2\rbrack$
So, other end$= \left( \frac{- 2}{1/2},\frac{- 2 \times - 2}{1/\sqrt{2}} \right)\ = ( - 4,\ 4\ \sqrt{2})$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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