Conic Sections Question 132
Question: If the line $ 2x+y+k=0 $ is normal to the parabola $ y^{2}=-8x $ , then the value of k will be
[RPET 1986, 97]
Options:
A) $ -16 $
B) $ -8 $
C) $ -24 $
D) 24
Show Answer
Answer:
Correct Answer: D
Solution:
$ y=-2x-k $ is normal to $ y^{2}=-8x $
or $ -k=-{-4(-2)-2{{(-2)}^{3}}}=-(8+16) $
therefore
$ \Rightarrow \frac{5}{3}=\frac{5}{2}(e^{2}-1) $ .
BETA
