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Question: Answered & Verified by Expert
If the line $y=m x+c$ is a tangent to the parabola $y^2=4 a(x+a)$ then $m a+\frac{a}{m}$ is equal to
MathematicsParabolaJEE Main
Options:
  • A $c$
  • B $2 c$
  • C $-c$
  • D $3 \mathrm{c}$
Solution:
2989 Upvotes Verified Answer
The correct answer is: $c$
Tangent at $y^2=4 a x$ is $y=m x+\frac{a}{m}$
Therefore, tangent at $y^2=4 a(x+a)$ is,
$y=m(x+a)+\frac{a}{m}$
or $y=m x+m a+\frac{a}{m} \Rightarrow m a+\frac{a}{m}=c$.

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