Conic Sections Question 434

Question: The latus rectum of a parabola whose directrix is $ x+y-2=0 $ and focus is (3, - 4), is

Options:

A) $ -3\sqrt{2} $

B) $ 3\sqrt{2} $

C) $ -3/\sqrt{2} $

D) $ 3/\sqrt{2} $

Show Answer

Answer:

Correct Answer: B

Solution:

Distance between focus and directrix is $ =| \frac{3-4-2}{\sqrt{2}} |=\frac{\pm 3}{\sqrt{2}} $

Hence latus rectum $ =3\sqrt{2} $ (Since latus rectum is two times the distance between focus and directrix).