Q15 / 92 · NTA Abhyas (JEE Main) 2020 · Mathematics · Parabola

If two parabolas y2=4ax-k and x2=4ay-k have only one common point P, then the coordinates of P are

  • Correct answer
    A
    2k,2k
  • B
    k,k
  • C
    a,2k
  • D
    k,2a

Solution

Parabolas y2=4ax-k and x2=4ay-k touch each other at the line y=x (∵ both parabolas are inverse of each other)
⇒y=x is the common tangent at P
⇒ we get point P by solving y2=4ax-k and y=x
⇒ point of contact P=2a,2a
⇒2a2=4a2a-k⇒k=a⇒P=2k,2k

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

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