Q94 / 160 · AP EAMCET 2019 (21 Apr Shift 2) · Mathematics

The normal at a point on the parabola y2=4x passes through (5,0). If two more normals to this parabola also pass through(5,0),  then the centroid of the triangle formed by the feet of these three normals is

  • A
    12,12
  • Correct answer
    B
    (2,0)
  • C
    (5,0)
  • D
    (0,2)

Solution

The given equation of a parabola,

y2=4x

The equation of normal at a point P(5,0)

y=-tx+2t+t3

0=-5t+2t+t3

3t=t3

t2=3

t=±3,0

Here, a=1

Co-normal point

Pat12,2at1=(3,23)

Qat22,2at2=(3,-23)

Rat32,2at3=(0,0)

The centroid is,

C=3+3+03,23-23+03

C=63,0=2,0

Hence, the correct answer is option: 'B'.

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