Q.

Let y2=12x be the parabola with its vertex at O. Let P be a point on the parabola and A be a point on the x-axis such that OPA=90°. Then the locus of the centroid of such triangles OPA is :      [2026]

1 y2-4x+8=0  
2 y2-6x+4=0  
3 y2-2x+8=0  
4 y2-9x+6=0  

Ans.

(3)

mAP=-t2

Equation of AP is

y-6t=-t2(x-3t2)

Put y=0

x=12+3t2

A(12+3t2,0)

Let centroid of OPA be G(h,k)

3h=0+3t2+12+3t2

      3k=0+6t+0

t=k2,    h=2t2+4

h=2(k24)+4

Locus of (h,k) is

y2=2x-8