Conic Sections Question 493
Question: The focal distance of a point on the parabola $ y^{2}=16x $ whose ordinate is twice the abscissa, is
Options:
A) 6
B) 8
C) 10
D) 12
Show Answer
Answer:
Correct Answer: B
Solution:
Let point be $ (h,k) $ . But $ 2h=k, $ then $ k^{2}=16h $
therefore $ 4h^{2}=16h $
therefore $ h=0,h=4 $
therefore $ k=0,k=8 $
$ $ Points are (0,0), (4,8).
Hence focal distances are respectively $ 0+a=4, $
$ 4+4=8 $ . $ (\because a=4) $
BETA
