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JEE Mains · Maths · STD 11 - 10.2 parabola,ellipse,hyperbola

Let the normal at the point \(P\) on the parabola \(y ^{2}=\) \(6 x\) pass through the point \((5,-8)\). If the tangent at \(P\) to the parabola intersects its directrix at the point \(Q\), then the ordinate of the point \(Q\) is

  1. A \(-3\)
  2. B \(-\frac{9}{4}\)
  3. C \(-\frac{5}{2}\)
  4. D \(-2\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(-\frac{9}{4}\)

Step-by-step Solution

Detailed explanation

Equation of normal : \(y =- tx +2 at + at ^{3} \quad\left( a =\frac{3}{2}\right)\) since passing through \((5,-8)\), we get \(t=-2\) Co-ordinate of \(Q :(6,-6)\) Equation of tangent at \(Q : x +2 y +6=0\) Put \(x=\frac{-3}{2}\) to get \(R\left(\frac{-3}{2}, \frac{-9}{4}\right)\)
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