Join the Most Relevant JEE Main 2025 Test Series & get 99+ percentile! Join Now
Search any question & find its solution
Question: Answered & Verified by Expert
If $x+y=k$ is a normal to the parabola $y^2=12 x$, then $k$ is
MathematicsParabolaJEE Main
Options:
  • A $3$
  • B $9$
  • C $-9$
  • D $-3$
Solution:
2820 Upvotes Verified Answer
The correct answer is: $9$
Any normal is $y+t x=6 t+3 t^3$. It is identical with $x+y=k$ if $\frac{t}{1}=\frac{1}{1}=\frac{6 t+3 t^3}{k}$ $\therefore t=1$ and $1=\frac{6+3}{k} \Rightarrow k=9$.

Looking for more such questions to practice?

Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.