Q.

Let a tangent to the curve y2=24x meet the curve xy=2 at the points A and B. Then the mid-points of such line segments AB lie on a parabola with the        [2023]

1 length of latus rectum 3/2  
2 length of latus rectum 2  
3 directrix 4x = 3  
4 directrix 4x = - 3  

Ans.

(3)

Let the equation of tangent to y2=24x  is ty=x+6t2

Now, ty=x+6t2 meets the curve xy=2  at points A and B.

Let mid-point of AB be (h,k)

ty=2y+6t2               [x=2y]

ty2-6t2y-2=0

y1+y2=6t

t·2x=x+6t2          [y=2x]

x2+6t2x-2t=0

x1+x2=-6t2

Midpoint P is (-3t2,3t)

h=-3t2, k=3t (h-3)=(k3)2y2=-3x