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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:

Option: 1

-3


Option: 2

-\frac{9}{4}


Option: 3

-\frac{5}{2}


Option: 4

-2


Answers (1)

best_answer

Equation of normal : \mathrm{y=-tx+2at+at^{3}}                     \mathrm{\because \left ( a= \frac{3}{2} \right )}

Since passing through \mathrm{\left ( 5,-8 \right )}, we get \mathrm{t=-2}

Co-ordinate of  \mathrm{Q:\left ( 6,-6 \right )}

Equation of tangent at  \mathrm{Q:x+2y+6=0}

Put  \mathrm{x=\frac{-3}{2}} to get   \mathrm{R=\left ( \frac{-3}{2},\frac{-9}{4} \right )}

Hence the correct answer is option 2.

Posted by

sudhir.kumar

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